Physical Restrictions

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

Physical restrictions on car use aim to reduce the volume of vehicles to achieve a more balanced allocation of road space. These measures can also improve the attractiveness of public transport, provide better facilities for cyclists and pedestrians, and improve environmental quality and safety.

However, demand impacts will vary according to the capacity of a network at the site where a physical restriction is implemented. If capacity is reduced on a few roads or areas but there is still capacity available on other routes, drivers may divert onto an alternative route which still has available capacity. This will reduce traffic congestion on a specific road, but not lead to an overall reduction in the level of car traffic in an urban area.

Introduction

It is obvious that, in many locations, road capacity is no longer sufficient to provide for unrestrained growth in car use, therefore the existing road capacity should be used in the best possible way aiming to reduce the present amount of traffic.

There are a lot of specific techniques that can be employed to limit or restrict the use of vehicles in a given area as a permanent measure or during specific periods of time. When implementing measures that limit or restrict vehicular access, simultaneously improvements should be implemented to other travel modes (or to take other mitigating actions) so that overall access to an area is not inhibited.

Generally, physical restrictions are implemented in order to achieve at least one of the following
three objectives: revitalisation of downtown areas, reduced congestion or reduced air pollution in specific localised areas or "hot spots." They are usually part of a broader programme to accomplish one of these three objectives.

Terminology

Physical restrictions limit car use in urban areas or other specific zones by reductions in road capacity such as street closures or reallocation of road capacity from cars to other traffic such as buses, cyclists and pedestrians. They include bus priorities, segregated cycle facilities, extensive pedestrian areas, street-running rail such as tram or light rail systems and also traffic calming measures. These cover all the measures to reduce or reallocate of road capacity. Most individual measures are covered in detail in a separate section. Restricted access to a defined area for certain types of traffic such as through traffic are covered in regulatory restrictions, which may not reduce road capacity overall but reduce capacity for particular vehicle movement.

Description

Styles of Physical Restrictions

Cairns et al (1998) collected over 60 case studies of reductions or reallocations of road capacity and classified these cases into several types. Based on their classification physical restrictions are distinguished into two styles:

Allocated to priority vehicles
Road capacity for car use is reallocated by introduction or extension of bus priorities, segregated cycle facilities and light rail systems. These measures generally aim not only to reduce car traffic volume but also to encourage the use of public transport to provide a frequent, punctual and reliable service.
Converted to other use
Road capacity for car use is reduced by changes or extension of a defined area (often a city centre) into a pedestrian area or car-free area, the closure of a particular street entering a city centre, and introduction of traffic cells in which a city centre is divided into cells, where car traffic movement between each cell (or entering from outer areas) is prohibited or restricted, based on limited entrance points. Some types of vehicles like buses and service vehicles are usually exempted from restrictions.

Temporary closure and reductions in capacity due to road or bridge repairs, maintenance work and natural disasters were also collected by Cairns et al (1998), because these cases provide relevant information about what drivers actually do in response to changes in availability of road space. However, these temporary measures do not target the reduction of car use, so they are not included in this section.

Technology

There are few specific technological requirements for the operation of physical restrictions, but urban traffic control (UTC) systems help the efficient operation of road capacity reallocation measures such as bus priorities and street-running rail. Public transport priority is one of critical objectives for UTC systems, in which buses or trams regularly travel through without stopping at junctions with traffic signals by selective vehicle detection systems (Fitzroy and Smith, 1993).

When access for public transport or other types of vehicle is permitted into a restricted area, the category of vehicles needs checking at the entry points, using paper licenses. Current access control technologies, which permits drivers to pass the point without stopping, are covered in regulatory restrictions.

Why introduce physical restrictions?

Reallocation of a proportion of road capacity - either to favoured classes of vehicle use or to non-vehicle use - is of major policy interest. Measures like: bus priority schemes, street-running rail systems, cycle lanes, wider footpaths and pedestrian areas, where well-designed and appropriate for their context, can help to achieve a more efficient use of road space, improve the attractiveness of non-motorised modes, increase accessibility to specific locations, bring about environmental improvements, enhance street attractiveness and improve safety.

SACTRA (Standing Advisory Committee on Trunk Road Assessment, 1994) concluded that increases in road capacity by new road construction in congested conditions were likely to induce extra traffic to an extent. In addition, it is generally difficult to provide sufficient new road capacity in most urban areas, so attention is focused on the role and the use of existing road capacity. Therefore it is expected that reductions in road capacity for car use will lead to some reductions or suppression in car traffic volume.

Demand impacts

The demand impacts of physical restrictions will depend on the types of implemented measures. Most changes decrease demand for car travel and conversely increase that for public transport, walking and cycling when road capacity for car use is reallocated by introduction of other transport priority measures. This will contribute to transport policy objectives seeking to reduce congestion and associated negative impacts. However, impacts vary according to the capacity of a network at the site where a physical restriction is implemented. The nature of the network and the existing level of congestion affect the ability of traffic to change route, vary journey time and make other responses. In some cases, when capacity is reduced on one road, but there is still available capacity on other routes or other times of the day, diverted trips such as re-routing and re-timing occur, and congestion spreads out over time and space rather than becoming worse on the treated road itself.

As Cairns et al (1998) described in their research, on over 100 places, located in the U.K., Germany, Austria, Switzerland, Italy, The Netherlands, Sweden, Norway, the U.S., Canada, Tasmania and Japan based on a range of methods comprising road-based and cordon-based traffic counts, roadside interviews, repeated cross-sectional travel surveys and panel surveys, the evidence showed a very wide range of results.

The sample of case studies showed an average reduction in traffic on the treated road or area of 41 per cent. Less than half of this reappeared as increased traffic on alternative roads, at the same or different times of the day. Therefore the average overall reduction in traffic was 25 per cent from the modified road or area. These averages were influenced by a few extreme results - in two cases the overall reduction in traffic was greater than all of the traffic originally travelling on the treated roads, and in seven cases there was an overall traffic increase.

The median result indicates that 50 per cent of cases showed overall traffic reductions of in excess of 14 per cent of the traffic which originally used the modified road.

Responses and situations
Response	Reduction in road traffic	Expected in situations
		Where the congestion increases in peak hours on the road where capacity is reduced for car use.
		Where the drivers need to divert from the route where capacity is reduced for car use.
		Though alternative destinations are not an objective of reduced road capacity, there is the potential for changing destination.
		Where there is potential to work, shop etc from home.
		Where public transport provides an attractive service, and cycle lanes or wider footpaths are available.
		Where modal shift and/or reduction in number of journeys makes owning a car uneconomic or impractical.
		In the long term committed individuals may move closer to frequent destinations or streets where it is possible to walk, cycle or use public transport.

	= Weakest possible response		= Strongest possible positive response
	= Weakest possible negative response		= Strongest possible negative response
	= No response

Short and long run demand responses

Demand response is different in the short, medium and long term.

In the first few days, there is a volatile and uncertain range of experience. It differs according to advance publicity and information, and there is a leaning period based on experience with a response each day, based on the changing experience of the previous day. In some cases there were longer queues and worse congestion, while in others no problems arose from the first day of implementation.

During the first few years, after the first adjustments, there tends to be a more settled period as traffic adjusts to new conditions. Flows tend to be variable with respect to weather or trend effects, but with levels no higher than previously.

In the longer run, case studies have revealed two different patterns. One pattern is a tendency for an initial traffic reduction to be offset by subsequent re-growth. In other cases the longer run effect is not an erosion of the traffic reduction but an intensification. For example, the longer run reductions in traffic are greater than those which occur at first (Cairns et al, 1998). The demand response will vary depending on which types of measures are implemented through the plan and whether more are phased in over time. Demand responses are completed on the basis of an overall decrease in car use. In principle, both scenarios can be consistent with an increase over time in the reduction in traffic due to the capacity reduction.

Demand responses
Response	-	1st year	2-4 years	5 years	10+ years
	-
	-
	-
	-
	Ride share
	-
	-

	= Weakest possible response		= Strongest possible positive response
	= Weakest possible negative response		= Strongest possible negative response
	= No response

Supply impacts

There are some decreases in the supply of road space for car use, where road closures or changes to pedestrian area are implemented to reduce road capacity, and bus priorities or cycle lanes are implemented to reallocate road capacity. Conversely, other transport facilities increase in supply like bus lanes, pedestrian areas and so on. However, total transport space usually does not change.

Financing requirements

The cost of physical restrictions depends on individual measures, but is usually cheaper than measures to increase road capacity. Reallocation of road capacity measures may require investment in operation of UTC systems. If access control is needed in reducing road capacity such as the closure of streets, investment and operating cost for the enforcement of access control technology may be needed. Reconstruction cost for pedestrian areas is sometimes needed.

Expected impact on key policy objectives

Physical restrictions are implemented to reduce car use and to promote using other transport. They encourage people to reduce their overall level of car traffic use in the city centre by switching from car to other modes. Also, they will contribute to a liveable, attractive and safe city centre. To see more detail on the impacts of individual measures, e.g. bus priorities, cycle lanes, traffic calming. However, if capacity is reduced on a few roads or areas but there is still capacity available on other routes, drivers may divert onto an alternative route which still has available capacity. This will reduce traffic congestion on a specific road, but not lead to an overall reduction in the level of car traffic in an urban area.

Contribution to objectives
Objective	Scale of contribution	Comment
	/	By reducing delays and improving reliability, depending on the scale of capacity reduction. However, by increasing diverted traffic around the area, efficiency may be reduced.
	/	The change of the closed roads into pedestrian areas will improve the streetscape and reduce community severance. However, the increase of diverted traffic around the area will worsen the environment.
		By reducing air and noise pollution and pressures on green space and environmentally sensitive sites when the closed roads are changed into pedestrian area. However, the increase in diverted traffic around the area may worsen the environment.
		By improving public transport services, improved conditions for walking and cycling; benefits from reduced congestion.
		By reducing traffic levels.
		New commercial developments within the newly created pedestrian areas.
		The cost of road capacity allocation, and investment and operating cost for UTC systems or access control technology is cheaper than measures to increase road capacity.

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

Expected impact on problems

Physical restrictions would reduce car use in urban areas, hence they have the potential to contribute to the alleviation of a number of key problems.

Contribution to alleviation of key problems
Problem	Scale of contribution	Comment
Congestion	/	By reducing car traffic volumes and providing reliable public transport services; however there will be an increase in diverted traffic.
Community impacts		By reducing traffic volumes and improving an attractive pedestrian area; however there will be an increase in diverted traffic.
Environmental damage		By reducing emissions of NOx, CO2 emissions, particulates and other local pollutants; however there will be an increase in diverted traffic.
Poor accessibility		By enhancing the reliability of public transport and by discouraging car-oriented development in a city centre.
Social and geographical disadvantage		By enhancing the reliability of public transport and reducing traffic levels.
Accidents		By reducing traffic volumes and/or improving a pedestrian area; however there will be an increase in diverted traffic.
Economic growth		By encouraging new activity in areas with reduced traffic.

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

Expected winners and losers

One would not expect everybody to benefit equally from any transport measure. Indeed, those who use priority transport modes should benefit from reduced congestion - by better bus services, improved conditions for walking and cycling and better air quality. However, unless effective measures of parking control and/or public transport are introduced there can be some losers through increased traffic congestion – e.g. persons forced to travel by a less preferred route, time or mode.

Winners and losers
Group	Winners/Losers	Comment
Large scale freight and commercial traffic		Where reduction of road capacity results in increase traffic congestion on routes used by freight vehicles, reducing utilization of freight vehicles making high value journeys.
Small businesses	/	Where reduced car use and introduction of pedestrian areas encourages use of local amenities, but where reduction of road capacity results in increased traffic congestion on routes used by small businesses.
High income car-users	/	High income associated with high value of time and thus continued car use for high value journeys. These journeys will benefit from reduced congestion, but will disbenefit from increased congestion.
All existing public transport users		Reduced congestion and priority measures of public transport will improve public transport reliability. In addition, where increased demand for alternatives results in increased quality and volume of service.
People living adjacent to the area targeted	/	Increased congestion on the routes with capacity reduction or on diversion routes, but priority measures of public transport will improve service of public transport.
Cyclists including children	/	Cyclists will benefit from the improved conditions for cycling in the targeted area. But they might be affected by increased congestion from the rerouted traffic in other areas.
People at higher risk of health problems exacerbated by poor air quality	/	Where car use is reduced car use and replaced with pedestrian areas, air quality will improve – lower emissions of NOx, CO2 emissions, particulates and other local pollutants. However there will be an increase in diverted traffic in other areas.
People making high value, important journeys		These journeys will have higher priority than others, and may continue to be made by car.
The average car user	/	Unless they benefit from reduced congestion.

	= Weakest possible benefit		= Strongest possible positive benefit
	= Weakest possible negative benefit		= Strongest possible negative benefit
	= Neither wins nor loses

Barriers to implementation

Scale of barriers
Barrier	Scale	Comment
Legal		There are no obvious legal barriers to the implementation of physical restrictions.
Finance		Physical restrictions can be implemented at low cost but UTC systems and access control system are sometimes required.
Governance		Implementation is usually the responsibility of a single agency.
Political acceptability		Politicians are often reluctant to reduce road space for car users.
Public and stakeholder acceptability		Reduction of road capacity for general traffic is likely to give rise to protests from local car users. However, pedestrians, cyclists and public transport users are likely to be supportive.
Technical feasibility		The nature of the network and/or urban fabric is the key feasibility issue.

= Minimal barrier

= Most significant barrier

Nottingham Zones and Collar, UK
Zurich, Switzerland
Gothenburg, Sweden
Freiburg, Germany

Nottingham Zones and Collar, UK

Display location

Concept of the zones and collar scheme (Vincent and Layfield, 1977).

Context

The Nottingham Zones and Collar scheme was introduced experimentally in 1975-76 at the western sector Nottingham by Nottinghamshire County Council, and aimed to selectively delay non bus traffic where queues would cause least disruption to buses, thereby encouraging car users to transfer bus. The main scheme features were:

Zone exit controls - traffic wishing to leave the two residential zones during the morning peak was restricted to certain exit roads most of which were controlled by traffic lights. The exit controls were designed to limit the rate at which traffic joined the main roads so that buses and other main road traffic could run more freely.
Collar controls - traffic lights on each of six main radial roads formed a partial collar of control signals around the city. The signals were timed to limit the traffic entering, and particularly passing through, the inner city area. It was intended that the traffic flows during the morning peak hour should be reduced by an average of about 10% below the August 1973 levels.
Bus priorities - to prevent bus passengers being delayed in the control queues, bus priority lanes were provided on the approaches to all the collar signals and to some zone exits. Exemptions from certain traffic regulation orders allowed buses to bypass delays at other zone exits by making turns banned to private vehicles or by using short sections of bus only street.
Park and ride - travellers for whom the conventional bus services were inconvenient could travel by car to one of four specially provided peripheral car parks and from there continue their journey by coaches operating a frequent, limited stop service into the city.

The zone exit controls with their associated bus priorities and the collar controls operated within the morning peak between 7:30 am and 9:30 am; certain of the bus lanes approaching the collar sites and two other bus lanes on the main roads operated also during the evening peak. Coach services to Park and Ride sites ran every 7.5 minutes during both peak periods, and it was possible to use nearby, normal service buses throughout the day.

Impacts on demand

Vincent and Layfield (1977) concluded that results showed the scheme failed to achieve its two main objectives - on the demand side discouraging travel by private vehicles, and on the supply side making travel by bus more attractive.

The main impacts on demand side are:

Average numbers of vehicles passing through six collar controls between 7:30 and 9:30 were 13,380 before and 13,150 after, in a decrease of only 1.7%.
Only about half the traffic leaving the two controlled residential zones experienced extra delays; these averaged just 1.0 to 2.5 minutes depending on location during the morning peak. On main radial roads between the outskirts and the city centre, the average journey times of traffic increased by no more than 1.5 minutes during both the morning and evening peak hours.
No significant changes were observed in transport mode by residential zones for journeys through the zone and collar controls to the inner city area, since the small improvements in bus journey times relative to those by car were largely counteracted by an increase in bus fares of 20-25% and a decrease in fuel prices of 20% between the surveys (both changes being in real terms after allowance for inflation).
It was found difficult to impose very long delays on traffic approaching the collar signals due to the restricted space for storing queues of vehicles. The maximum delays produced were about three or four minutes depending on site.
The scheme produced a redistribution of traffic between the main radial roads leading into the city, but this resulted in little increase in vehicle kilometres.
There was a decrease in through traffic taking shortcuts through the residential zones, but the effect on total traffic in the zones was small.
Park and ride had little effect on traffic congestion. The removal of cars from inner city roads was negated by the Park and Ride buses, each of which removed only 3.3 cars on average.

Impacts on supply

The main impacts on supply side are:

The scheme reduced bus journey times between the residential zones and the city centre by less than on a minute on average during the period of enforcement.
The punctuality of buses was not improved, but bus priorities largely protected buses from the effects of the restricted measures.
Two bus priority lanes during the evening peak, produced savings averaging 1.5 to 2 minutes per bus. The overall saving in bus time due to these two evening peak bus lanes was greater than that observed during the morning peak period when a total of ten bus lanes and various other priority measures were operational on the surveyed routes.

Contribution to objectives

Contribution to objectives
Objective	Scale of contribution	Comment
		A net disbenefit estimated to be roughly £54,000 (in 1975) for one year of operation of the scheme starting August 1975 was produced by the zone and collar scheme, consisting mainly of extra delays to private and commercial traffic which substantially outweighed the benefits to bus passengers.
		A decrease in through traffic taking shortcuts through the residential zones improved liveability.
		No estimation has been made, but probably slightly worse because of higher congestion.
		There was little or no contribution to meeting equity and social inclusion objectives because public transport services were little improved. However, essential car users suffered from the delays since they had no alternative.
		Records of personal injury accidents were obtained for two years before and one year during the experiment, but no significant change in accidents was detected while the experiment was in operation.
		No analysis has been conducted.
		The scheme cost approximately £280,000 for the one year of operation including loan charges on about £330,000 capital expenditure mainly for new traffic signals, signs, and markings and for the park and ride sites.

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

Zurich, Switzerland

Context

Fitzroy and Smith (1993) report the performance and main features of the operation of road reallocation in Zurich. During the 1950s and 1960s the trams and buses had been criticised as slow and unreliable, despite the long history of tram use. Delays arose from private vehicle obstruction such as cars turning at junctions and being forced by parked vehicles to drive along the tramlines. To augment public transport speeds and improve reliability, a package of measures was introduced, based on approval of a city referendum in 1977. The aim was to ensure that the road space allocated to public transport was well defined and unobstructed. To facilitate the smooth operation of the segregated track, several complementary actions were initiated:

prohibition of parking and waiting on 15 road stretches;
28 no-left-turns at junctions with roads used by trams;
the banning of private cars and taxis from selected zones;
the presence of a sufficient number of uniformed police to enforce restrictions.

The road space allocated to public transport consists mainly of the 117.3 km, 13-route tram network. There are also 19.2 km of reserved lanes for diesel buses (compared to 2.6 km in 1976) out of a city network of 89.7 km, and 36.3 km of trolleybus lines. The benefits of segregated track lie in the length of the exclusive lanes and the strictness with which they are enforced.

After the several years of this implementation, a computer guided signaling system was installed to ensure that punctuality is maintained and waiting time is minimised for public transport. In addition, all public transport mode season tickets (Rainbow) were introduced throughout the city in 1985, freely transferable across family members or friends.

Impacts on demand

From 1960 to 1977, the number of trips by public transport was fairly stable at just below 200 million per year. Thereafter this grew steadily to around 210 million per annum between 1982 and 1984. From 1985 trips rose dramatically to about 280 million in 1990, which represents 33% growth in six years. This was mirrored by a stabilisation in number of car trips on main roads since 1981. However, Rainbow ticket introduction was chiefly responsible for the rapid climb between 1985 and 1990.

Impacts on supply

The combined effect of these measures reduced average journey durations. It was estimated that 8.2 km stretch of one tram route took 36 minutes to traverse during the evening peak period in 1970. By 1991, this had fallen to 32.5 minutes for the same journey at the same time of day.

Contribution to objectives

The Zurich scheme was introduced to improve public transport services as a package of measures and there was no evidence of an effect on the vehicle traffic volume (Fitzroy and Smith, 1993). The contribution to objectives shown in the table below is based on the assumption that the main objective was to improve public transport.

Contribution to objectives
Objective	Scale of contribution	Comment
		No analysis has been conducted, but the improvement of public transport services should have increased efficiency, as long as delays to other users did not offset this.
		No analysis has been conducted.
		No analysis has been conducted.
		Improvements in public transport have made the transport environment more equitable and reduced the potential for social exclusion through lack of access to a car.
		No analysis has been conducted, but prohibition of roadside parking and no-left-turns at junctions should have decreased accidents.
		No analysis has been conducted.
		The cost of road capacity allocation is not reported, but it is thought to be significant because of wide area implementation.

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

Gothenburg, Sweden

Display location

Gothenburg city centre divided into cells (Cairns et al, 1998)

Context

Cairns et al (1998) and Vuchic (1999) cover Gothenburg as a case study. In 1970, the closure of the CBD to unauthorised vehicles was implemented at weekends since severe traffic and environmental problems had become apparent. In 1970-72, the CBD was divided into five cells, whose boundaries could not be crossed by private vehicles. The cells were surrounded by an inner ring road, which acted as a bypass for through traffic, and allowed entry and exit to and from the sectors. Only pedestrians, cyclists, public transport and emergency vehicles were allowed to cross the boundaries between the areas.

Figure 1 – Polycentrism in Gothenburg. Source: HLJ 2015 Transport policy in Nordic urban regions - POLISE

In 1973-74, it was planned to extend the zoning concept to the whole of the Central Urban Area (CUA) divided into two cells by a North-South screenline. Between 1970 and 1980, other policies were also put in place: three major central streets were pedestrianised and many streets were made one-way. The proportion of the tram network running on reserved tracks was increased from 65% to 90%, and other public transport was given some priorities on-street and at signals. In 1979, a comprehensive traffic policy was put into place, to manage traffic, to improve the attractiveness of other modes, to complement the existing cells, and to try to reduce vehicle flows, partly to facilitate implementing further cells. By 1988, the number of parking spaces in the CBD had been cut from 21,000 to 14,000, and parking charges were increased by up to 100% (an equivalent of about €1.0/h at 1988 prices).

As a result, car traffic in the city centre was halved. This change is considered a trend change because public transport and pedestrians and bicycle traffic were now given priority in the centre of Gothenburg.

Impacts on demand

	1970	1975	1979	1982
Across CBD boundary	150,000	100,500	93,000	82,500
Across CUA boundary	320,000	320,000	316,800	300,800

(Cairns et al, 1998) (unit: vehicles/day)

There was obviously a substantial decrease in traffic entering the CBD and CUA. The North-South screenline across the CUA recorded 25,265 vehicles in 1971, and 26,690 vehicles in 1983, an increase of 5.6%, with a marked shift of traffic towards the completed route to the north of the CBD. This means that through traffic increased, transferring onto the remaining available routes. The increase in through traffic was much less than traffic increases in the rest of Gothenburg, so that the cells might have both suppressed car trips for which they were the destination, and suppressed traffic growth in the area generally.

As a result of the CBD cells, total vehicle kilometres for private traffic increased by about 7%, but with no increase in vehicle hours, as changes to junctions made flows more efficient. In addition, the introduction of cells stimulated public transport use and pedestrian movements in the CBD.

Gothenburg
Figure 2 – Source: HLJ 2015 Transport policy in Nordic urban regions - POLISE

Impacts on supply

The cell system itself has not affected supply, but other measures such as the pedestrianisation of major streets, one-way streets, increases in the proportion of the tram system on reserved tracks and traffic in the traffic cells has reduced the road capacity for car use. In addition, parking space was reduced in the CBD.

Contribution to objectives

Contribution to objectives
Objective	Scale of contribution	Comment
		In the first year in the CUA, accident reductions were estimated to be 2.2 million SEK, public transport time saving 2.0 million SEK and extra vehiclekilometres -0.5 million SEK.
		No analysis has been conducted, but the reduction of congestion should have improved liveability.
		Noise and air pollution have declined in the CBD zones. In the CUA zones, a third of residents enjoyed a decrease in noise of up to 8dBA, one third were not affected, and one third experienced an increase in noise of up to 4dBA, although largely only 1-2 dBA. Overall there was a decrease in the amount of noise experienced by residents.
		No assessment of equity impacts has been made.
		In the CBD zone, between 1970 and 1982, traffic accidents fell by 45% within the zones.
		No analysis has been conducted.
		The new cells of the CUA and associated measures cost 5.8 million SEK.

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

Freiburg, Germany

Display location

Freiburg city centre and major roads (Cairns et al, 1998)

Context

Cairns et al (1998) covers Freiburg as a case study for good planning practice. Most roads in the city centre were closed to motor vehicles by the end of the 1970s, when parts of the major ring road around the city centre were widened from 2 to 4 lanes. The main city centre road was closed for car use, but trams and buses were allowed to enter the city centre. During the late 1980s, some of the capacity on the ring road was reallocated to cycle lanes and cycle paths. The width of the car lanes was reduced by 1-1.5 metres for the cycle lanes. In 1996 some parts of the ring road (Rotteckring and Werderring) were reduced from 4 lanes to 2 lanes, and 2 lanes were changed into two way bus lanes, at the same time a parallel road (Bismarckallee and Schnewlinstrasse) was widened to 4 lanes with a cycle lane.

Impact on demand

The following table shows the changes to one day traffic flows on major city centre ring road. (Cairns et al, 1998)

Road	Nov87	Nov95*	Feb96**	Apr96***	May96	Nov96	Feb97	Jun97
Eschholzstr	23.0	22.9	21.1	22.0	21.8	22.5	20.6	20.8
Bismarckallee	24.8	0.4	15.3	23.0	23.7	30.7	25.3	26.0
Rotteckring	33.5	41.1	34.2	27.2	27.0	28.2	22.6	23.2
Schlossbergring	31.5	29.3	28.0	30.3	30.5	33.5	27.9	29.6
Total	112.8	93.7	98.7	102.6	103.0	115.1	96.3	99.6

(unit: 1000 vehicles)
* In Nov. 1995 Bismarckallee and Schnewlinstrasse were closed.
** In Feb. 1996 Bismarckallee was opened with 2 lanes.
*** In Mar. 1996 Rotteckring was reduced to 2 lanes and Bismarckallee was extended to 4 lanes.

This table shows a 12% decline of traffic flows on the major city centre ring roads in ten years despite a significant growth in the number of vehicles in Freiburg from 350 per 1000 population in 1977 to 487 per 1000 in 1996, an increase of nearly 40% in 20 years. However, these changes resulted in a reduction in traffic on the treated roads of 34%, of which a large proportion was observed on the alternative routes provided. The overall effect was a reduction in traffic of about 7% of the traffic formerly using the treated sections.

In 1976, 22% of all trips into the city were made by public transport, 18% by bicycle and walking and 60% by vehicle, and in 1995 modal share has changed to decrease car use, with 26% by public transport, 28% by bicycle and walking and 46% by vehicle.

Impact on supply

In Freiburg, overall road capacity has been reduced overall since 1970s for reallocation to bus or cycle, but some road capacity reductions were associated with expanding the capacity of alternative routes in order to maintain the supply of road space.

Contribution to objectives

Contribution to objectives
Objective	Scale of contribution	Comment
		No analysis has been conducted, but the reduction in vehicle traffic and a increase by bicycle and walking should have increased efficiency provided that the reduction in capacity did not increase congestion.
		No analysis has been conducted, but a increase by bicycle and walking and 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, but increased facilities for walking, cycling and public transport should have been beneficial.
		No analysis has been conducted, but an increase by bicycle and walking on dedicated facilities should have improved safety.
		No analysis has been conducted.
		No evidence regarding costs, but the expenditure on new road construction should have been significant.

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

Gaps and weaknesses

Long distance diverted traffic may occur outside the studied area. Any omission of these diversions would be likely to result in an overestimate of traffic reduction.

Physical restrictions have not always been implemented to meet simple objectives: one is to reduce the traffic volume; the other is to improve the attractiveness of public transport. As a consequence, it is sometime difficult to isolate which specific measure is effective or ineffective within physical restrictions even though the main cause of the change is clear in the case studies. Individual measures covered in separate sections help to illustrate this.

Contribution to key objectives
Objective	Nottingham	Zurich	Gothenburg	Freiburg

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

Contribution to alleviation of key problems
Objective	Nottingham	Zurich	Gothenburg	Freiburg
Congestion
Community impacts
Environmental damage
Poor accessibility
Social and geographical disadvantage
Accidents
Economic growth

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

Appropriate contexts

Physical restrictions may be more appropriate in high density business and residential areas because public transport can be supplied there by more attractive services. However, when there is still available capacity on other routes, diverted trips occur and congestion spreads out in space.

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

* Where there is a congestion problem.

Adverse side-effects

There are no significant adverse side effects which are not addressed above.

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