Traffic Calming Measures

This measure was fully updated by THE ASSOCIATION FOR URBAN TRANSITION - ATU in 2014 under the CH4LLENGE project, financed by the European Commission.


Traffic calming is the use of physical and regulatory measures to reduce vehicle speeds and acceleration. Its other aims are to alter driver behaviour and improve conditions for non-motorised street users. It focuses upon improving neighbourhood safety, comfort and liveability, whilst maintaining necessary levels of traffic circulation and emergency access. It encompasses a broad array of traffic engineering, education, and enforcement techniques to slow and disperse or re-route traffic.

The concept originated in the Dutch ‘Woonerf’ schemes of the 1970s when individual streets were reconstructed to tip the balance in favour of a residential function of the streets and to reduce the domination of motor vehicles. Since then traffic calming has been extended to numerous countries (particularly in northern Europe, Australia and North America) and used not only for particular streets but also across whole areas, e.g. city centres.

Traffic calming measures/devices can be separated into two types based on the main impact intended:

  • segregation (volume control measures), in which extraneous traffic is removed;
  • integration (speed control measures), in which traffic is permitted, but encouraged to respect safety and the environment.

A combination of segregation measures can create a ‘maze’ or ‘labyrinth’, which makes through movement difficult (e.g. median barriers, one-way streets). Their primary purpose is to discourage or eliminate through traffic and hence divert it to surrounding streets. The extra traffic on surrounding streets can add to congestion and environmental intrusion there, and this trade-off needs to be carefully considered at the design stage. However, the maze treatment also reduces accessibility for those living in the area, and this loss of accessibility has often led to the rejection of such measures by residents whom they are designed to benefit.

Integration measures are designed to encourage the driver to drive more slowly and cautiously. By making routes through residential areas slower, they can have a more direct impact on speed and hence safety, but will also induce re-routing to major roads, and hence a reduction in environmental impact. Such benefits may again be offset by increases in congestion and environmental impacts on the diversion route.

The evidence from case studies suggests that traffic calming is particularly effective in improving the ‘liveability’ of streets, providing additional protection to the local environment and reducing the incidence and severity of accidents. It is less effective in improving efficiency and stimulating economic growth but the overall trade-off would suggest a positive outcome from the implementation of traffic calming measures providing they have been carefully designed.

Traffic calming devices

Terminology

The ITE (Institute of Transportation Engineers) Subcommittee on Traffic Calming states that "Traffic calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior and improve conditions for non-motorized street users". (Trafficcalming.org)

Traffic calming focuses on improving neighbourhood safety, comfort and livability, while maintaining necessary levels of traffic circulation and emergency access. It encompasses a broad array of traffic engineering, education, and enforcement techniques to slow and disperse or re-route traffic.

The solutions proposed to reduce the traffic speeds and volumes and favour the non-motorised modes have been refined with time. If early traffic calming measures (used from the 1970s onwards) focused more on the laws of physics and applied to one or few streets, the more recent applications in countries that already have a long history of traffic calming rely more on human psychology (intend to influence the driver’s ‘state of mind’ and generate a responsible-informal behaviour) and have the tendency to extend to large areas or to be applied differently according to the characteristics of each city area. The more recent understanding of traffic calming has often materialised in the design and development of ‘shared spaces’ and operates on the principle that all transport modes must equitably share the given street space, thus resulting in priority for pedestrians and cyclists. Examples of shared spaces are:

  • the Dutch ‘woonerf’ – the shared space ‘pioneer’ developed in the 1970s and followed by different versions developed in northern Europe, among them the  British “home zone”
  • the Swiss ‘Begegnungs­zonen’ – in UK known as ‘encounter zone’ and in France as ‘zone de rencontre’
  • the ‘Berner model’ – applied starting in the 1990s for some towns located within Bern’s periphery.

Well known cases of shared space in the UK include New Rd, Brighton; Exhibition Rd in London; the ring road in Ashford, Kent; and Poynton, south west of Manchester.  The two latter cases are very interesting because they are on arterial roads with high traffic volumes and in the final case involved the removal of traffic signals at a major junction.  Informative videos about all of these schemes are available on www.youtube.com
Though traffic calming refers mainly to physical measures and devices altering streets’ configuration for the purpose of slowing motorised traffic, it now includes any measure/initiative that slows traffic and encourages pedestrians and cyclists onto the roadway while making the drivers more aware of their presence. Examples include inexpensive and easy-to-implement measures, related to temporary alterations or additions to the street appearance or temporary changes in its use such as:

  • painting designs or patterns on the street (traffic circles, crosswalks, etc.);
  • placing artworks, furniture or other objects in the middle of the roadway;
  • coating the roadway in a rough surface;
  • changing the colour or design of building enclosures and façades;
  • temporarily changing the use of parking spaces or the roadway.

Reducing speed limits to 30km/h (or 20mph) is often used as a means of traffic calming, but is principally introduced to improve safety and is covered under accident remedial measures. There is often a direct connection to traffic calming, however, since many speed reduction schemes use traffic calming – in the case of DfT (2009), it was estimated that 96% of England’s then 2,150 20 mph zones had humps or other traffic calming measures.  There is an increasing trend to introduce 30km/h (20 mph) zones on arterial roads as well as on residential streets, although here more normally without vertical measures to reduce speeds.  For example, most arterial routes in the city of Oxford, England, have 20 mph speed limits in the city centre and where they pass through and form part of district centres in the city’s suburbs. The City of Berlin has been a pioneer in Germany in the widespread use of 30km/h zones on its arterial streets (see City of Berlin, 2013) to cut noise and improve safety.

Description

Traffic calming measures can be separated into two types based on the main impact intended:

  • segregation (volume control measures), in which extraneous traffic is removed;
  • integration (speed control measures), in which traffic is permitted, but encouraged to respect safety and the environment.

Trafficcalming.org summarise these measures in the following table. Other individual measures are reviewed in Hass-Klau et al (1992) and IHT (1997) as well as in UK Local Transport Note 1/07 (2007).

Segregation

Full Closures

Half Closures

Diagonal Diverters

(Volume Control)

Median Barriers

Forced Turn Islands

One Way

Integration

Speed Humps

  • round-top humps
  • flat-top humps
  • sinusoidal profile humps
  • ‘H’ road humps
  • ‘S’ road humps
  • thermoplastic hump (‘thumps’)
  • speed cushion
  • mechanical humps

(Speed Control)

Speed Tables

Raised Crosswalks

 

 

Raised Intersections

Textured Pavement

Intersection Islands

 

Roundabouts

Chicanes

Realigned Intersections

 

Intersection Narrowings

Pinch Points

Centre Island Narrowings

 

Chokers

Gateways

Planting

 

Street Furniture

Bar Markings

 Rumble devices (rumblewave)

 

Mini Roundabouts

 

 

(Based on Trafficcalming.org, and complemented from Hass-Klau et al (1992) IHT (1997) and Local Transport Note 1/07) (Note that US and European terminology may differ.)

A combination of segregation measures can create a 'maze' or 'labyrinth', which makes through movement difficult. Their primary purpose is to discourage or eliminate through traffic and hence divert it to surrounding streets. The extra traffic on surrounding streets can add to congestion and environmental intrusion there, and this trade-off needs to be carefully considered at the design stage. However, the maze treatment also reduces accessibility for those living in the area, and this loss of accessibility has sometimes led to the rejection of such measures by the residents whom they are designed to benefit (McKee and Mattingly, 1977). An alternative approach, more often used in city centres, is the traffic cell, in which an area is divided into cells, between which traffic movement, except perhaps for buses and emergency vehicles, is physically prohibited.  These measures are considered further under Physical Restrictions.

Integration measures are designed to encourage the driver to drive more slowly and cautiously. They can be divided into three groups: vertical deflections, horizontal deflections and narrowing. It is clear that these can achieve significant reductions in speed and accidents (Abbott et al, 1995; Barbosa et al, 2000). By making routes through residential areas slower, they can also induce re-routing to major roads, and hence a reduction in environmental impact (Sumner and Baguley, 1979). Such benefits may be offset by increases in congestion and environmental impact on the diversion route.

In contrast to the traffic control measures implemented in the 1980s, ‘shared space’ is achieved by removing all traffic signs, lights and other traffic control devices from the street space. The former are replaced by a streetscape that “speaks” to the driver through surface materials, building enclosure, on-street parking, trees and shrubs, art and decoration. Thus, the daily traffic is regulated by informal social-street rules and responsible travel behaviour. The aim of this approach, developed by the Dutch engineer Hans Monderman, is to enable common use of the available street space. In brief, the shared space concept rests on the idea that taking away traffic regulation elements generates a certain feeling of insecurity, which is assumed to lead to a higher attention level and thus to safer street user behaviour, and negotiation between users about how each uses the space.

Technology

Traffic calming measures are not dependent on technology, but some categories of vehicles such as buses and emergency vehicles may need protected access into a physically restricted area. Current access control technologies, which permit such vehicles to pass the point without stopping, are covered in regulatory restrictions.

Why introduce traffic calming?

The concept of traffic calming is primarily concerned with reducing the adverse impact of motor vehicles on built up areas. This usually involves reducing vehicle speeds, providing more space for pedestrians and cyclists, and improving the local environmental quality. Traffic control devices such as speed limit signs are regulatory measures that require enforcement. By contrast, traffic calming measures are intended to be self-enforcing. Traffic calming measures may have many objectives (Traffic Calming for Communities):

  • achieving slow speeds for motor vehicles;
  • reducing collision frequency and severity;
  • increasing the safety and the perception of safety for non-motorised users of the streets, thereby increasing walking and cycling to realise health benefits;
  • reducing the need for police enforcement;
  • enhancing the street environment (e.g., street scaping);
  • increasing access for all modes of transport and
  • reducing through motor vehicle traffic.

Traffic calming can be a way of resolving potential conflicts and competition for road-space but it has to be developed in an integrated way. Some specific policy issues may be involved (IHT, 1997):

  • Routes for buses
    Specific attention needs to be paid to the design of traffic calming measures on bus routes, because, for example, road humps appear to be a problem for bus passenger comfort and safety and for vehicle maintenance. This can be solved partially by the use of speed cushions that allow wider vehicles to straddle them, with less of a speed reducing effect, whilst cars are still slowed.
  • Disabled pedestrians
    Shared space facilities which reduce the distinction between footway and roadway may pose a hazard for blind and partially sighted pedestrians and, potentially, for children.
  • Cyclists
    Traffic calming is an appropriate means of facilitating cycling, as lower speeds and flows can lessen the need to separate cyclists from motorized traffic. However, any of the physical means/devices employed to slow traffic have the potential to create problems for cyclists. The latter are more vulnerable to any lack of attention to detail in design of traffic calming measures than are occupants of motor vehicles. Narrowings and pinch points were identified by cyclists as sensitive points because, when carriageway width is reduced, motorists tend to pass cyclists with less clearance (Gibbard et al., 2004). A cycling bypass should be the first option to introduce where a narrowing is introduced on a road. Cyclists also noted that the ramps of some humps and raised intersections can be uncomfortably steep. It this case a smooth slope and a smooth transition between the horizontal and slopping surfaces should be ensured (Local Transport Note 1/07).
  • Motorcyclists
    Motorcyclists’ speeds may not be influenced as effectively as those of larger vehicles, and care will be needed to avoid excessive speed. At the same time, it is important to ensure that physical measures do not impose a safety hazard for motorcyclists.
  • Routes for emergency service vehicles
    There is concern that the cumulative effect of the growing number of traffic calming schemes could compromise the ability of fire and ambulance service operators to meet the required response times. There have also been suggestions that traffic calming features might unwittingly lead to increased patient discomfort, or cause damage to equipment carried in ambulances or fire appliances (Local Transport Note 1/07). Therefore, it is of high importance to maintain good access and a rapid response time for emergency services.  Again, the use of speed cushions can assist here.
  • Routeing of heavy goods vehicles
    Heavy goods vehicles should be encouraged to remain on the highest available category of route for as much of their journey as possible. Traffic calming can be used to control speeds but the largest size of vehicles involved needs to be taken into account.
  • On-street parking
    Provision for the required levels of on-street parking should form an integral part of the design of all traffic calming and parked vehicles themselves can sometimes assist in reducing traffic speed, if they are sited in appropriate locations – for example, when parallel parking is changed to end on parking on alternate sides of the road in order to reduce sightlines and create chicanes.
  • Economic development
    Traffic calmed areas have potential for economic growth and development and this can be a positive encouragement to shopping and other commercial activity, as the progressive pedestrianisation of town centres, and also the traffic calming of district centres (but without the removal of through traffic), have both demonstrated.
  • Main roads
    Successful traffic calming requires a road hierarchy framework. Traffic calming techniques may be appropriate on main roads where drivers need to be encouraged to proceed at a pre-defined speed in a calm and safe manner.
  • Safe routes to school
    Community representatives and school authorities should be consulted to ensure that traffic calming proposals can assist children on their journey to school.

Demand impacts

Traffic calming measures reduce vehicle traffic speeds and volumes, so that the main impacts of these measures can be to improve the environment and livability and to reduce accidents. The purpose of segregation measures is to discourage or eliminate through traffic, but to induce diversion to other roads. The additional distance travelled is likely to add only marginally to the cost of the journey, however, and hence to have little impact on the number of journeys by car. Only where the network is close to capacity is demand likely to be reduced.

Responses and situations
Response Reduction in road traffic Expected in situations
n/a
Where the drivers can divert from the calmed streets or roads.
/ Where traffic calmed areas can be less attractive and so discourage shopping; but can have potential for economic growth and development by pedestrianisation/improved pedestrian environment.
Motorised trips can be reduced where traffic calming makes the street environment safe enough that more people feel comfortable making short local trips on foot, for example to school or the local shops.
By providing a safe and comfortable, pleasant environment for cyclists and pedestrians (see above).
n/a
Evidence (e.g. Bretherton Edwards and Miao, 2000) shows that the impact of traffic calming in the US on property values was statistically random.
= Weakest possible response = Strongest possible positive response
= Weakest possible negative response = Strongest possible negative response
= No response

Short and long run demand responses

It is unlikely that there will be significant change in demand response of traffic calming over time.

Demand responses
Response - 1st year 2-4 years 5 years 10+ years
-
  - / / /
  Change job location
- Shop elsewhere (preferably in the local area) neighborhood)
- Go on foot/bike to school in the neighborhood
  Compress working week
- Trip chain
- Work from home
- Shop from home
  Ride share
- Public transport
- Walk/cycle
  -
  -
= Weakest possible response = Strongest possible positive response
= Weakest possible negative response = Strongest possible negative response
= No response

Supply impacts

The main impact on supply of traffic calming is to reduce the capacity of the road network. The scale of this will be greatest where traffic calming measures are applied to main roads. Reductions in capacity are also likely to be sizeable where segregation measures, using mazes or traffic cells, are implemented. In these cases, the connectivity of the minor road network is reduced, and through traffic and some local traffic is forced to use the main roads. The impact will depend on the extent of the measures, but it is possible to envisage reductions in capacity of as much as 10%. With integration measures, the impact on capacity will be much less, since the minor roads are still available routes when demand is at the highest.

Financing requirements

The cost of traffic calming varies according to the measures and countries. Where considerable environmental measures are used to complement the physical measures the cost rises significantly. Costs for different types of measure have been quoted over a 30 year period and, in the absence of current data, are cited below without adjusting them for inflation.

The Dutch "Woonerf" required the reconstruction of the street and the removal of kerbs and footways to achieve a common shared space and were therefore very expensive, typically over £25 per square metre of road in the mid 1980s, which has constrained their widespread use. More recently, the construction of a high quality shared space over a 200 metre length of New Rd, Brighton, cost around £1.75 million in 2007 (see http://www.civicengineers.com/our-work/new-road-brighton); and on Exhibition Rd, London, the 20,000 square metre shared space scheme implemented in 2011 cost £25 million.  Clearly, these costs preclude the use of shared space over wide areas.

An indication of traffic calming costs, based on mid-1980s prices, from a selection of schemes in the Netherlands and Germany, range from under £1 per square metre of street area to over £100. The "standard" traffic calming techniques such as plateaus, gateways, junction treatments and planting fall into the £5-£20 per square metre range (Harvey, 1992).
 
The following table provides an indicative cost of road humps in 2007. The costs given for round-top and flat-top humps are based on those with tapered edges, so that additional drainage is not required. A kerb-to-kerb flat-top hump suitable for a pedestrian crossing would cost more because drainage is required. Traditional blockwork materials suitable for conservation areas can cost more, and any narrowing of the road would add further to the cost. Gully costs can be significant, in the order £1000. (Local Transport Note 1/07, p.57)

Hump type

Cost (£)

Round-top hump

400–1000

Flat-top hump

500+

Raised junction

10,000 approx.

‘S’ hump

2000

‘H’ hump

2500

Thermoplastic hump (thump)

300–500

Speed cushion

240–700

Pair of speed cushions

500–2000

 (Local Transport Note 1/07 ‘Traffic calming’)

The cost of rumble devices schemes can vary with the type of device and the number of strips or bands used. From the schemes studied it would appear that the typical range for a thermoplastic installation was £500–1500, at 1993 prices. Coarse aggregate rumble areas cost £2500–10,000 at 1992 prices and had an estimated life of about three years. Rumblewave surfacing costs c. £50 per square metre or c. £5000 for a 20 metres strip on a single carriageway road. (Local Transport Note 1/07, p.69) 

The following table provides sample US cost estimates for various traffic calming measures. These estimates cannot replace detailed cost estimates using quantities and local unit prices for work items associated with specific projects. The estimates in this table may be useful in conceptual planning, as they show order of magnitude differences among measures. Costs increase quickly when measures require landscaping, drainage improvements, or land acquisition (ITE and FHWA, 1999).

Types

Measures

Cost Estimate (US$)

 
   

Portland

Sarasota

Seattle

Segregation

Full Closures

-

-

120,000

(Volume Control)

Half Closures

40,000

-

35,000

 

Diagonal Diverters

-

-

85,000

 

Median Barriers

10,000 - 20,000

-

-

Integration

Speed Humps

2,000-2,500

2,000

2,000

(Speed Control)

Speed Tables

-

2,500

-

 

Raised Intersections

-

12,500

-

 

Traffic Circles

10,000 - 15,000

3,500

6,000

 

Chicanes

-

-

14,000

 

Center Island Narrowings

8,000 - 15,000

5,000

-

 

Chokers

7,000-10,000

-

-

(ITE and FHWA, 1999)

Expected impact on key policy objectives

The immediate purpose of traffic calming is to reduce the speed and volume of traffic. Reductions in traffic speed and volume are just means to other ends such as traffic safety and active street life, livability and the local environment, but can also induce re-routing.

Contribution to objectives

Objective

Scale of contribution

Comment

  By reducing capacity and by rerouting.
  / By improving streetscape and urban design and by reducing community severance; but streets or roads to which traffic in diverted may be worse.
  / By reducing air and noise pollution. However, diverted traffic may worsen the environment elsewhere.
  By improving accessibility for local people and those on foot or bicycle.
  By reducing speed of vehicles by implementing speed control measures.
  / By improving more attractive location for safety and environmental quality. However, traffic calmed areas can also be less attractive by reducing accessibility for visiting traffic.
  Costs vary depending on the design of the scheme.
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

Expected impact on problems

As with impacts on objectives traffic calming measures has potential to contribute to the alleviation of a number of key problems through reduction of the speed and volume of traffic, but the scale of contribution is dependent on the individual measures.

Contribution to alleviation of key problems

Problem

Scale of contribution

Comment

Congestion

By reducing capacity and by rerouting.
Community impacts By reducing traffic speed and flows.
Environmental damage / By reducing traffic-related emissions from reducing traffic speed; however there will be an increase elsewhere from diverted traffic; and some physical devices induce noise, although evidence shows an overall reduction in noise due to reduced traffic speeds
Poor accessibility / Accessibility will be improved for pedestrians and cyclists; there may be some reduction for vehicle users.
Disproportionate disadvantaging of particular social or geographic groups By disadvantaging these outside the area.
Number, severity and risk of accidents By reducing traffic speed.
Suppression of the potential for economic activity in the area By improving more attractive location for safety and environmental quality. However, traffic calmed areas can be less attractive due to reduced accessibility for visiting traffic.
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

Expected winners and losers

Winners and losers

Group

Winners/Losers

Comment

Large scale freight and commercial traffic

Where reduction of speed results in increased delay on routes used by freight vehicles, reducing utilisation of freight vehicles making high value journeys. Unlikely to be a major impact since traffic calming implemented over short distances

Small businesses

Where accessibility falls in some local areas, but economic activity may be improved by pedestrianisation.

High income car-users

Where they may suffer from reduced accessibility.
People with a low income Where they may suffer from reduced accessibility.
People with poor access to public transport May improve access to public transport by making walking journey to stops safer and more pleasant.
All existing public transport users Where road humps may make bus passengers uncomfortable.
People living adjacent to the area targeted Where reducing speed and volume of traffic inside the area can improve safety and environments, but the outside will suffer from diverted traffic.
Cyclists including children / By reducing speeds and improving street layout.
People at higher risk of health problems exacerbated by poor air quality By reducing pollution.

People making high value, important journeys

These journeys will have higher values of time and may continue to be made by car, but may be subject to more delay due to reduced accessibility.
The average car user Where they may suffer from reduced accessibility.
= Weakest possible benefit = Strongest possible positive benefit
= Weakest possible negative benefit = Strongest possible negative benefit
= Neither wins nor loses

Barriers to implementation

There are potentially severe barriers to implementation, particularly financial and related to feasibility. Legal barriers may also be serious in cases where the current planning legislation would need amendment for this instrument to be implemented.

Scale of barriers
Barrier Scale Comment
Legal In countries where legal definitions of and guidance on traffic calming exist, there is no major legal barrier to its use.  In some countries, however, there is no such definition and/or guidance and here any authority trying to implement traffic calming will face problems.  This is an issue in Poland, for example.
Finance Basic traffic calming measures can be implemented at low cost, especially in comparison to construction of new road or public transport infrastructure, or ITS.  However, if a traffic calming scheme also seeks to enhance the streetscape with new high quality materials and a major redesign of the cross-section of a street, costs in London average around £500 per square metre (2012).
Governance Traffic calming can usually be implemented by a single department within an authority.
Political acceptability Any perceived decrease in accessibility can be controversial for the residents within the treated area, and diversion of traffic for those outside.  However, the continued spread of traffic calming in most jurisdictions indicates that this is a barrier that can be overcome and surveys show that the majority of those living in traffic calmed areas are satisfied with the measure.
Public and stakeholder acceptability Acceptance by the local community and cooperation of relevant institutions is a key feasibility issue. Aesthetics and the precise location of calming measures are often important influences on acceptance.
Technical feasibility There are no obvious technical barriers.
= Minimal barrier = Most significant barrier

This section in the main presents results from case studies of traffic calming.  However, these case studies do not have data on the impact on every objective of traffic calming, so a short summary from a variety of studies is presented first.

Road safety

There is very strong evidence that traffic calming that effectively reduces speeds also leads to a significant reduction in injury accidents, even taking into account the impact of reduced traffic flow that often results from traffic calming schemes.  The following table is taken from DfT (2007), page 58, where it is numbered as Table 4.3.  It shows reductions in vehicle speeds to be expected from simple road hump-based traffic calming schemes, based on evaluations of more than 100 schemes in the UK in the 1990s.  A further analysis of a large number of schemes showed an average 50% reduction in injury accidents, with the general lesson being that every 1.6 km/h reduction in mean motor vehicle speeds led to a 5% reduction in injury accidents, with a particularly beneficial effect on injury accidents involving vulnerable road users.  In a Swiss case, the suburb of Köniz in Bern (2006), the redesign of an arterial shopping street let to a 3 km/h reduction in speeds, a 33% reduction in accidents and a 40% reduction in injuries, whilst traffic flows remained the same (DIFU, 2014).

Emissions and noise

The Köniz example cited above also saw a reduction in noise levels along the street of 2.2 dB(A), equivalent to the human ear of reducing traffic levels by a third (when in fact traffic flows did not change at all).  DfT (2007), referring mainly to humps and cushions, states that the noise reduction impacts of traffic calming vary considerably depending on the proportion of heavier vehicles in the traffic flow and the specific form of hump.  Essentially, the speed reducing effect of humps reduces noise from cars but may increase it at the site of the hump for heavier vehicles.  Hedström’s (1999) work in Sweden also confirms this and notes that the spacing of humps is important to maintain constant vehicle speeds; if they are too far apart, the resulting acceleration and deceleration erodes noise and emissions benefits.

Public health and social equity impacts

There are clear road safety benefits from traffic calming, as reported above (and see also for example Edwards, 2010).  There are fewer studies of public health impacts.  Morrison et al (2004) carried out a before and after survey of the impacts on health and community well-being of a main road traffic calming scheme in a deprived area on the outskirts of Glasgow.  They found statistically significant improvements in perceived road safety and reduction in nuisance reported from traffic (but an increase in other neighbourhood nuisances) together with increased pedestrian activity.  Physical health also improved.  In terms of the social equity impacts of traffic calming schemes, it is known that injury accident rates are higher in more socially deprived segments of society.  A study by Grundy et al (2007) of 300 traffic calming schemes in London found that they did not have greater effects in more deprived areas, although their introduction may have slowed the rate of increase in the gap between injury accident rates in more and less deprived areas.

Property values

Bretherton et al (2009) could find no relationship between traffic calming and property values – traffic calming can be found in very expensive and very cheap areas for property, so it seems to have no clear effect.  On the other hand, Litman (1999) cites studies suggesting that a 5% reduction in traffic flows once below 2,000 vehicles per day leads to a 1% increase in property values, and an 8 to 16 km/h reduction in speeds to a 5% increase in property values.

Local economic development

Compared to residential areas, there are fewer examples of traffic calming being implemented on shopping streets where it might be expected to have more direct economic development benefits, and there are therefore fewer evaluations of such effects.  Drennen (2003) found that most retailers on a traffic calmed shopping street in the Valencia area of San Francisco perceived it to have had beneficial effects on their businesses some four years after implementation, although the effects were not quantified.  DfT (2007, 2011) found evidence that traffic calming schemes make people feel safer and that they use the street more as pedestrians.  This in turn increases pedestrian footfall in the area.  There is clear evidence from e.g. Loveday (2006) that increases in footfall improve the local economy.  A specific case is the calming of and improvement of the pedestrian environment on Walworth Rd, London, where anecdotal evidence cited by CABE (http://www.cabe.org.uk/case-studies/walworth-road/description, accessed 28 July 2014) suggests that footfall increased and shop vacancy rates fell after the implementation of the scheme.  The economic development impacts of main road traffic calming schemes on shopping streets are also evaluated in  DfT (2008).

Liveability

Liveability is rather problematic to define in a rigorous way, but one can take as a proxy the way in which people use their street after it is traffic calmed, and feel about safety on that street.  DfT (2011) found statistically significant increases in perceived pedestrian safety in four of the five areas traffic calmed in Birmingham, England in the Inner City Road Safety Demonstration Project.  DfT (2007) cite various studies that in conclusion show that traffic calming schemes appear to improve perceived safety, and consequently make parents more willing to allow their children to walk on their own.  However, there is less evidence that adults walk more or that children play more in the traffic calmed streets.  

Traffic on parallel non-calmed routes

DfT (2007) cites a study of 48 traffic calming schemes that recorded an average reduction of 18% in traffic levels on the calmed streets – so traffic calming clearly has this beneficial effect in the treated areas.  Evidence to show whether this traffic simply diverts to parallel routes, or changes mode or destination, is much less clear cut.  The Köniz example, above, resulted in no major changes to traffic flows.  Cairns et al (1998) found that from a review of 100 empirical examples of capacity reductions on roads in urban areas, there was an average 25% reduction in the total flow in the whole area of the capacity reduction, not just on the specific road where capacity was reduced.  Therefore, the capacity reduction on a specific (e.g. traffic calmed) road did not have the sole effect of shifting traffic on to non-calmed parallel routes – in many cases, the opposite.

Political and public acceptability

There are examples in the UK of physical traffic calming measures being removed in a few municipalities due to specific political campaigns led by vociferous drivers, and a resulting change in political control in the municipality.  However, in general, the number of traffic calmed zones continues to increase across Europe and this is an indication that they are publicly acceptable.  Experience from a 2007 survey Edinburgh of residents living in traffic calmed zones found that 78% of residents surveyed thought 20 mph zones were ‘a great idea’, both before and after implementation.  A 1998 study of 45 UK schemes (Webster, 1998, cited in DfT, 2007) found that on average 65% of those surveyed approved of the schemes. This covered all users, including drivers.

Nuremberg, Germany

Context

Hass-Klau et al (1992) describe the process of traffic calming measures implemented in Nuremberg. Nuremberg was one of the first towns in Germany which decided upon large-scale pedestrianisation schemes in 1972. During the 1980s, pedestrianisation was extended step by step, and a large number of city centre streets were traffic calmed. However, it was still possible to cross the town centre by car in an east-west direction and vice versa, so the city decided to close the east-west route in 1988.

By the end of the 1980s it was still possible to travel through the town centre in a north-south direction and vice versa. The 1991 plan determined that no motor vehicle traffic through the centre would be possible. But the results of the 1991 plan have not been reported.

Impacts on demand

When the pedestrianisation scheme opened in 1972, 80% of the motor vehicle traffic disappeared and could not be accounted for in parallel streets. After the road closure in 1988, motor vehicle counts in parallel streets revealed that 29%, had transferred to these streets, and 71% of the traffic had disappeared.

Nuremberg started with a very large pedestrianisation scheme. When it become clear that little increase in traffic flows occurred in the parallel roads, the city become more and more confident over the years that a substantial reduction in motor vehicle traffic in the city centre, and also in some of the inner city areas, was the right way forward.

Impacts on supply

The objectives for supply side in the 1991 plan were:

  • creation of five traffic cells;
  • further increase in pedestrianisation;
  • reduction of car parking spaces for non-residents;
  • increase in residents parking;
  • 30km/h speed limit everywhere in the city centre;
  • increase of car parking charges from 1DM to 5DM per hour (about £ 2 at 1991 prices)

Contribution to objectives

Contribution to objectives
Objectives Comment
 

The road closures should have reduced efficiency for car use (though it appears that most traffic has disappeared). Pedestrianisation and cycle lanes would have improved efficiency of cycling and walking.

 

An increase by walking and cycling and a reduction in vehicle traffic will have improved liveability.

 

No estimation has been made, but the reduction in vehicle traffic should have reduced air and noise pollution.

 

During the 1980s, a lot of progress was made in building cycle facilities and Nuremberg has an excellent cycle network and a relatively large number of cyclists (11% of the flow in the city centre).

 

Pedestrianisation and cycle lanes should have improved safety for pedestrians and cyclists.

 

In the road closures of 1988, the traders claimed that they would lose trade. They actually lost on average about 20% of their turnover. However, in the 1991 plan the traders have understood that restricting private cars is necessary, and even good for business (Hass-Klau et al, 1992). By providing a more attractive location, economic activity will have improved.

 

No evidence regarding costs.

= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

20 mph zones in Edinburgh, Scotland

Context

In its 2000 Local Transport Strategy the Edinburgh City Council set an objective of meeting national targets of a 40% reduction in people killed and seriously injured in road collisions by 2010 on a 1994-98 base.  It used traffic calming, in the form of mainly self-enforcing 20 mph zones (so with humps and speed cushions) in order to achieve this.  Mackenzie (2008) evaluated the impact of 112 of these schemes on injury accidents as reported by the police.

Impacts on demand and supply

As noted above, 120 schemes were introduced over a 9 year period 2000-2008.  The impacts on traffic demand are not known.  By 2008 the zones covered approximately 30% of the built up area of this city of 454,000 people; they have continued to be extended since, including an area-wide scheme on all non-arterial roads in South Edinburgh introduced in 2013.  The zones consist of vertical traffic calming measures to reduce the need for police enforcement.

Contribution to objectives
Objectives Comment
 

No data available on impacts on congestion or traffic flows.

 

78% residents in zones supported idea before and after implementation

 

No data on environmental impacts

 

No assessment of equity impacts has been made.

 

36.6% reduction in injury collisions in residential areas
35.9% reduction in injury collisions around schools.
42% reduction in injury collisions in residential areas

All based on 3 years’ before and 3 years’ after data and 112 schemes.  Reduction faster than that for Scotland overall over same period.
 

Impossible to disaggregate impacts of traffic calming on economic growth from other much more macro-economic influences such as global banking crisis, national economic growth and so on.

 

120 zones implemented 2000-2009 in Edinburgh cost £6.7 million.  Reduction in injury collisions repays this investment within 1-2 years.

= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

District shopping centre scheme, Newlands Avenue, Hull, England

This scheme and its impacts are reported in DfT (2008) and DfT (2011).  Newlands Avenue is a district shopping centre in Hull in England.  A 0.9 km length of the road was treated to improve the shopping environment and reduce casualties.  A median strip was placed in the road, a number of raised tables were built to provide formal and informal crossing points, speed cushions were installed elsewhere, footways were widened, loading relocated onto side streets, and echelon parking created at points of high parking demand.  A 20 mph speed limit was introduced on the main street to complement the existing 20 mph zone in the surrounding residential streets.  The scheme was implemented in 2005 at a cost of £1.75 million.   The impacts were as follows (before data gathered in 2004 and after in 2006, unless otherwise stated):

  • There was a 54% reduction in all injury accidents (reported 2011).
  • Speeds were recorded northbound and southbound at 21 points on the route.  Before, speeds exceeded 20 mph at 15 of these points in both directions.  This fell to two points in the after survey.  In addition, speeds were more consistent in the off-peak especially.
  • Journey times for private vehicles along the route fell at all times southbound, and at all times except afternoon peak in the northbound direction
  • Pedestrian footfall rose by over 20% on both sides of the road.
  • Pedestrians crossing the road using formal crossings rose by 25%, and the number of pedestrians with mobility problems crossing the road rose by 15%.
  • House prices in the area rose by more than the average for Hull.
  • Nitrogen oxide levels decreased by 15% at all four measuring sites on the route.
  • Public transport boardings increased overall on the route.

Full details of the scheme and its impacts are available from http://webarchive.nationalarchives.gov.uk/20090511090853/http://www.dft.gov.uk/pgr/roadsafety/dpp/mpr/schemereports/kingston.pdf.

Contribution to objectives
Objectives Comment
 

Scheme improved traffic flow whilst also increasing footfall, so it was doubly efficient in economic terms.

 

Above average increase in house prices.

 

Reduction in NOx.  No monitoring of PM10.

 

Increase in use of street by people with mobility problems.

 

Significant reduction in injury accidents.

 

No after data available apart from on house prices.

 

£1.75 million for 900 metres of road approx. 12 m wide.  Reduction in injury collisions repays this investment within a few years.

= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

San Diego, US

Context

Ewing (1999) reports the effective and ineffective choices of traffic calming measures in San Diego.

Street network inviting through-traffic at Mira Mesa in San Diego

Figure1: Street network inviting through-traffic at Mira Mesa in San Diego (Ewing, 1999)

Vehicle users pass Mira Mesa streets to travel between inland and coastal communities (see Figure 1). There are few east-west arterials in that part of San Diego, and those few had become congested enough to cause vehicle users to divert to alternative routes. Five residential collectors had become problematic, affected not only by high traffic volumes but also by the excessive speeds that often accompany through traffic.

At the request of the Mira Mesa Community Planning Committee, the city first tried peak-hour turn restrictions to discourage shortcutting. The restrictions did not work. Vehicle users found ways to circumvent them through U-turns and other manoeuvres. The city then installed speed humps. The hump profile chosen was the 12-foot parabolic hump.

Street network inviting through-traffic at Royal Highlands in San Diego

Figure 2: Street network inviting through-traffic at Royal Highlands in San Diego (Ewing, 1999)

The Royal Highlands neighbourhood, sandwiched between two arterials and a freeway in San Diego, also had a through traffic problem (see Figure 2). Traffic would filter through the neighbourhood on one of four local residential streets. The first attempt at traffic calming was the installation of 12-foot speed humps. While closely spaced and severe in profile, the humps were not sufficient to counter the strong incentive to cut through the neighbourhood. Then further traffic calming, full road closures, was also implemented.

Impacts on demand

The humps in Mira Mesa were successful in the limited sense of reducing through traffic on four collectors and reducing vehicle speeds on all five (Table 1). However, they were not successful in a more general sense because new problems were created. Fire response times were degraded by the treatment of Capicorn Way. Traffic was diverted from collectors to parallel local streets that were less well designed to deal with it. The one local street for which before-and-after data were available experienced a 34 percent rise in traffic volume and a nine percent increase in its 85th percentile speed.

Table 1: Traffic on collectors before and after speed hump installation in Mira Mesa (Ewing, 1999)

Traffic Calmed Collector

Daily Volume

(Vehicles per day)

85th Percentile Speed

(miles per hour)

 

Before

After

Before

After

Aquarius Drive

5,940

3,250

38

25

Avenida Del Gato

2,960

1,250

38

25

Bootes Street

5,710

4,660

36

30

Capicorn Way (Camino Ruiz-Orion Way)

6,870

6,860

34

25

Capicorn Way (Orion Way-Camino Ruiz)

11,540

11,040

36

25

Libra Drive

5,580

2,660

38

27

The main effect of the humps of the first attempt in the Royal Highlands was to divert traffic to the local street closest to the neighbourhood's northern entry point, Dellwood Street. The Dellwood route offered the fewest humps end-to-end. However, the second attempt was more successful. After closing the northern entry point at Armour Street, traffic volumes on all local streets fell below their initial levels. The neighbourhood now has speed controls (which did not solve the through traffic problem) and a volume control (which apparently was effective).

Table 2: Traffic before humps, after humps, and after closure in Royal Highlands (Ewing, 1999)

Street

 

Vehicles Per Day

 
 

Before Speed Humps

After Speed Humps

After Street Closure

Armour Street

525

350

280

Caledonia Street

215

240

210

Dellwood Street

1,065

1,260

370

Kirkcaldy Street

1,350

820

260

Lochlomond Street

140

180

90

Total traffic within neighborhood

3,295

2,850

1,210

% change in total traffic

-

-14

-63


Impacts on supply

In the case of Royal Highlands, road capacity was reduced by half due to the closures implemented in Armour Street.

Contribution to objectives

Contribution to objectives
Objectives Comment
  The reduction of road capacity and rerouting reduced efficiency.
  A reduction in vehicle traffic should have improved liveability.
  No estimation has been made, but the reduction in vehicle traffic should have reduced air and noise pollution.
  No assessment of equity impacts has been made.
  Decreased speeds will have decreased a number of accidents and improved safety for pedestrians, cyclists and cars travelling next to each other.
  No analysis has been conducted.
  No evidence regarding costs.
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

Local towns, UK

Context

The County Surveyors Society (1994) reviewed 152 case studies and provided more detail of the 85 case studies of traffic calming implemented in the late 1980's and early 1990's in the UK. The numerical analysis which follows draws on all the 152 case studies submitted.

Just over half the schemes (56%) were located in urban residential area with 29% occurring on main roads in rural locations and the remaining 15% in town centre areas.

74% of the schemes were aimed at reducing speed, with 64% aimed at accident reduction, and 36% at reducing the volume of through traffic. Nearly every scheme was intended to address two of these problems and many were aimed at all three. Environmental improvements were sought in 17% of the schemes, fairly evenly spread over the three types of location.

76% of the schemes used more than one type of speed controlling device. Some schemes involved a whole range of different types of measures. Road humps in one form or another were included in 66% of the schemes submitted and were by far the most commonly used technique. The next most popular technique was some form of carriageway narrowing, with 41% of schemes using this method. Chicanes featured in 26% of schemes and 17% of the schemes included refuges, mini roundabouts, road markings and signs. Other relatively commonly used measures were gateways (10%), table junctions (9%), coloured surfacing and rumble strips (6%).

Impacts on demand

The following table gives example results in the case studies for "Town Centre Areas".

Location

Traffic Volume

(veh/day)

Speed

(mph)

Accidents

(pia pa)

Cost

(£k)

 

Before

After

Before

After

Before

After

 

West Sussex Horsham

-

-

35

15

3

0

2,300

Northamtonshire Rushden

2,540

2,080

24

17

3.7

2

230

Herfordshire Borehamwood

18,800

16,500

26

20

15

8

1,200

Cambrigdeshire Eaton Socon

10,700

8,900

38

32

19

4

130

Cornwall Saltash

9,000

7,900

32

17

6

1

230

Devon Bamstaple

1,800

4,000

23

11

0.25

0.25

3

Essex Southend on Sea

-

-

28

26

28

9

181

Kent Gillingham

5,000

5,000

-

-

1.3

0.7

18

Kent Rochester

8,000

4,000

35

25

2

0

18.5

Isle of Wight Ryde

850

815

29

18

0

0

14.5

Warwickshire Leamington Spa

15,600

17,500

-

20

3

5

35

Warwickshire Rugby

7,100

5,400

50

25

2

0

69

Note: Comparative subjective comments are given regarding effectiveness. These are based on the following indicative criteria which may differ from individual authorities' own criteria options:

Effectiveness should be assessed against the scheme objectives which can vary greatly. However, the effectiveness of the measures employed seems to vary considerably and it is not certain whether this is the result of differences in design or of location. From the schemes sent in was in not possible to identify any one specific measures as more or less effective. Effectiveness, it seems, will depend on the way measures are fitted to local conditions and on the combination of measures used (County Surveyors Society, 1994). Single measures were judged as of moderate cost of £3,000-£10,000, reasonable of £10,000-£20,000 and expensive over £20,000. For several measures moderate cost were £5,000-£50,000/km, reasonable were £50,000-£100,000/km and expensive over £100,000/km.

Impacts on supply

Most schemes reduced road capacity for vehicle use and also limited vehicle speed.

Contribution to objectives

Contribution to objectives
Objectives Comment
  The reduction of road capacity and rerouting reduced efficiency.
  No analysis has been conducted, but a reduction in vehicle traffic should have improved liveability.
  No estimation has been made, but a reduction in vehicle traffic should have reduced air and noise pollution.
  No assessment of equity impacts has been made.
  In most town centres, accidents reduced by a significant or considerable amount.
  No analysis has been conducted.
  Costs of each measure are given on the table.
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

Gaps and weaknesses

There is limited evidence on impacts on public transport, especially bus services. If journey times on a bus route passing through traffic calmed streets are increased significantly because of the implemented measures, this will reduce the attractiveness of the service.


Contribution to key objectives
Objective

Nuremberg

Edinburgh

San Diego

UK Towns

Newlands Ave Hull

  -
 
 
  - - -
 
  - -
 
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

 

Contribution to alleviation of key problems
Problem

Nuremberg

Edinburgh

San Diego

UK Towns

Newland Ave Hull

Congestion
Community Impacts
Environmental damage
Poor accessibility - - - -
Social or geographic disadvantage - - -
Accidents
Economic growth - -
= Weakest possible positive contribution = Strongest possible positive contribution
= Weakest possible negative contribution = Strongest possible negative contribution
= No contribution

Appropriate contexts

Traffic calming originally was developed for local residential areas, but these measures have been extended to shopping areas, village centres, school entrances and other sensitive locations The 1980s saw the first attempts to introduce traffic calming measures on main urban roads, mostly at places where shopping and commercial activity was concentrated. The creation of effective schemes is usually more difficult in such locations than in residential areas because of the greater intensity of pedestrian and other activity, and thus greater competition for the available space (Pharaoh and Russell, 1991).

Hass-Klau et al (1992) surveyed 385 traffic calming schemes in UK. They summarised the type of area (as defined by the local authority) as follows. Traffic calming was most commonly applied to minor roads in suburban residential areas (34% of all schemes) whereas only 14% were on main roads in the same type of area. 15% were implemented on minor roads in inner city residential areas. A small proportion (6%) was carried out on other inner city roads, especially shopping streets. 29% were either in other areas or not identified. Most of the schemes (88%) comprised only a small number of streets, usually only one street, and few were installed or planned on an area-wide basis (12%).

Appropriate area-types
Area type Suitability
City centre
Dense inner suburb
Medium density outer suburb
Less dense outer suburb
District centre
Corridor
Small town
Tourist town
= Least suitable area type = Most suitable area type

Adverse side-effects

Some traffic calming measures reduce accessibility in the area. However, by making routes through the areas slower, they can also induce re-routing to major roads, and hence a relocation of environmental impact.

A widespread problem exists between traffic calming the need of ambulances, fire appliances and buses. These need to be addressed well before consultations take place on individual traffic calming projects (County Surveyors Society, 1994).

Abbott, P.G., Hartley, S., Hickman, A.J., Layfield, R.E., McCrae, I.S., Nelson, P.M., Phillips, S.M. and Wilson, J.L. (1995) The environmental assessment of traffic management schemes: A literature review. TRL Report 174. Crowthorne. TRL.

Barbosa, H. M., Tight, M.R. and May, A.D. (2000) A model of speed profiles for traffic calmed roads. Transportation Research A 34 103-123.

Bretherton, W. Edwards, M. and Miao, J. (2000) The Economic Impact of Speed Humps on Housing Values.  ITE Journal, January 2000.

Cairns, S., C. Hass-Klau and P. Goodwin. Traffic Impact of Highway Capacity Reductions: Assessment of the Evidence. Landor Publishing, London, 1998*.

City of Berlin (2013) Evaluierung von Tempo 30 an Hauptverkehrsstraßen in Berlin (Evaluation of 20mph limits on main roads in Berlin).  City of Berlin Administration for City Development and Environment.

County Surveyors Society (1994) Traffic calming in practice. Landor publishing, London.

Department for Transport, Department for Regional development (Northern Ireland), Scottish Executive, Welsh Assembly Government -  Local transport note 1/07 ‘Traffic calming’ (March 2007)
http://www.ukroads.org/webfiles/LTN%201-07%20Traffic%20Calming.pdf

DfT 2008 Mixed Priority Routes Newlands Avenue Hull Demonstration Project Report.  WSP/DfT, London, available at http://webarchive.nationalarchives.gov.uk/20090511090853/http://www.dft.gov.uk/pgr/roadsafety/dpp/mpr/schemereports/

DfT, 2009 Review of 20 mph Zone and Limit Implementation in England.  Road Safety Report.  DfT, London.

DfT (2011) Mixed Priority Routes Update Results Report.  DfT, London.

Drennen, E (2003) Economic Effects of Traffic Calming on Urban Small Businesses
Thesis, Department of Public Administration San Francisco State University

Edwards, P (2010) The Health Effects of 20 mph speed zones.  Report to London Road Safety Unit.  London School of Hygiene and Tropical Medicine, UK

Ewing, R. (1999) Traffic calming: State of the Practice. ITE (Institute of Transportation Engineers) and FHWA (Federal Highway Administration). (http://www.ite.org/traffic/tcstate.htm)

Gibbard A, Reid S, Mitchell J, Lawton B, Brown E and Harper H (2004). The effect of road narrowings on cyclists. TRL Report 621, Transport Research Laboratory, Crowthorne.
http://www.transport-research.info/Upload/Documents/200607/20060728_163846_65628_UG171_Final_Report.pdf

Grundy, C et al (2007)  The Effect of 20 mph zones on Inequalities in Road Casualties in London Report to London Road Safety Unit.  London School of Hygiene and Tropical Medicine, UK

Hass-Klau, C., Nold, I., Bocker, G. and Crampton, G. (1992) Civilised streets: A guide to traffic calming. Brighton, Environmental & Transport Planning.

Harvey, T. (1992) Review of current traffic calming techniques. PRIMAVERA. (http://www.its.leeds.ac.uk/projects/primavera/p_calming.html)

Hedström, R. (1999) Miljöeffekter av 30 km/h i tätort – med avseende på avgasutsläpp och buller - en förstudie (Environmental effects of 30 kmh zones in built up areas, with a focus on exhaust emissions and noise: an initial study)  VTI Report 869, Linköping, Sweden.

IHT (Institution for Highways and Transportation) (1990) Guidelines for Urban Safety Management.

IHT (Institution for Highways and Transportation) (1997) Transport in the urban environment. Chapter 20 Traffic calming and the control of speed.

Litman, T (1999) Traffic Calming Benefits, Costs and Equity Impacts.  VTPI, Victoria, Canada.

Loveday, M. (2006) The Economic Impacts of Walking.  Paper to Walk21 Conference, Melbourne.

McKee, W.A. and Mattingly, M.J. (1977) Environmental traffic management - The end of the road? Transportation 6(2) 365-377.

Macdonald, M and Mackenzie, G (2012) A study into the effectiveness of traffic-calming measures in residential and school zones in Edinburgh.  Paper to Annual Scottish Public Health Conference, Crieff, 2012.

Morrison D. S., Thomson H. and Petticrew M. (2004) Evaluation of the health effects of a neighbourhood traffic calming scheme.  Journal of Epidemiology and Community Health 58 pp 837–840

Pharaoh, T.M. and Russell, J.R. (1991) Traffic calming policy and performance: The Netherlands, Denmark and Germany. Town Planning Review 62 79-105.

Sumner, P. and Baguley, C. (1979) Speed controls on residential roads. LR 878. Crowthorne. TRRL.

Links

Fehr & Peers Associates, Trafficcalming.org (http://www.trafficcalming.org/)

Institute of Transportation Engineers, Traffic calming for communities (http://www.ite.org/traffic/)