Variable Message Signs
- Summary
- Taxonomy & description
- First principles assessment
- Evidence on performance
- Policy contribution
- References
This measure was fully updated by INSTITUTE FOR TRANSPORT STUDIES (ITS) in 2014 under the CH4LLENGE project, financed by the European Commission.
Variable Message Signs (VMS) are digital road signs used to inform car drivers about specific temporary events and real-time traffic conditions. The signs are often linked to a manned control centre via a local network or a radio link. Variable message signs (VMS) are an integral part of Intelligent Transportation Systems.
The aim of using VMS is to provide drivers with mandatory and/or advisory information at the roadside. VMS can be used for many different purposes with the potential benefits of reducing car drivers’ stress, travel time and increasing traffic safety. VMS may ask drivers to change travel speed, change lanes, divert to a different route, or simply to be aware of a change in current or future traffic conditions by providing information, direct to the available parking space – see also Parking Guidance Systems. The information is intended to assist drivers in selecting appropriate routes avoiding congestion and to reduce drivers’ anxiety.
The benefits of the signs in general are difficult to measure. VMS are often used to inform drivers of congestion, incidents ahead and unexpected delays and can as such reduce drivers’ stress. Signs can be particularly beneficial where drivers can be informed of alternative routes or park and ride sites to avoid further delays, but this may require the VMS to be an integral part of a wider and more costly traffic monitoring system. One major study suggests that drivers would like to see VMS used more. Some evidence indicates that VMS are not likely to distract drivers if designed properly. A reduction in the number of violations of speed limits can be expected where ‘SLOW DOWN’ signs are put up, but as yet there is little firm evidence of the safety benefits of VMS in general.
The main barrier to implementation is cost. Some concerns may be also raised about visual intrusion of new signs. However, by reducing the number of static road signs it is suggested that properly designed VMS can reduce negative aesthetic impacts. The costs of VMS are made up of purchase, operating and maintenance. Costs vary significantly depending of type of sign and the appropriate data and sensors required to compute an appropriate message to drivers.
Variable message signs (VMS) are an integral part of Intelligent Transportation Systems. VMS can be used where greater flexibility is required than can be offered by fixed direction or advisory signs. VMS are used to deliver on road information to drivers in real-time, with the aim of improving traffic safety and efficiency.
In its simplest form a Variable Message Sign could be a manually operated device saying ‘full’ or ‘empty’ on a board, as seen on manned car parks. Normally VMS is a term employed to electronic signs, controlled via a computer. Whatever the sophistication of the technology, the message displayed on the VMS needs to be understood by all, so the quality of the message is important.
VMS is also known by various other names including:
- DMS: Dynamic Message Signs;
- CMS: Changeable Message Sign;
- EMS: Electronic Message Sign;
- VAS: Vehicle Activated Sign.
A VAS is for example a sign which detects and warns speeding vehicles on the approach to bends or speed limits or high vehicles on approaches to low bridges (see DfT 2003 for more information).
Technology
VMS are generally linked to a manned control centre. The controller transmits information to be displayed in a coded way through one-to-one communication links, a local network or via radio communication.
The types of VMS range from simple one or two line text message signs to fully variable signs that can include graphical displays. The sign designer needs to consider a number of factors, including sign-size, character height, legibility, contrast and viewing angle. Messages must be comprehensible to the vast majority of drivers. Use of VMS is increasing in response to more complex traffic management requirements and the need for more information to be provided to drivers.
VMS currently employ three general types of technology (IHT, 1997):
- Electro-Mechanical signs involve rotating planks with two faces or prisms with three faces which are usually used to give versatility to a standard fixed-face traffic sign.
- Reflective flip-disk signs are made up of a matrix of disks, one side black, the other fluorescent. The momentary application of an electrical current will magnetically ‘flip’ a disk between the ‘on’ and ‘off’ states. These signs are well suited to showing combinations of letters or symbols as a message.
- Light emitting signs normally use fibre-optic, magnetic flip disc or light-emitting diode (LED) technologies. The major advantage of these signs is that a greater range of message can be displayed than for reflective technology signs. LEDs, being solid-state devices, can also produce very good reliability with minimal maintenance.
Further developments may lead to applications based on Liquid Crystal Display (LCD), matrix band, liquid dot matrix and micro shutter technologies (ERTICO, 1998). It is feasible to combine technologies within the same sign. When used as warning signs, it is usual for them to be fitted with amber-flashing lanterns.
VMS is often used with other technologies; for example a variable message display could show a different price for different times of the day or if connected to a camera monitoring device, a different price depending on the level of congestion on the road.
Two restrictions on VMS are the limitation of the panel to display data (number and size of characters and pictograms) and the temporal correctness of the information provided. Only limited information can be presented to the driver. Further there are concerns that VMS can cause driver distraction and so create a safety risk (Erke et al. 2007). Another problem is that the messages displayed may not be completely understood by all drivers, and so pictograms are preferred to text messages (ERTICO, 1998).
Operation of VMS
The UK Highways Agency opened an English National Traffic Control Centre in 2003, delivering information through Variable Message Signs and in-car systems. The Scottish National Driver Information and Control System (NADICS) covers an area from Inverness to Gretna and Edinburgh to Glasgow in Scotland. A number of UK local councils have installed VMS as part of accident reduction strategies. Variable Message Signs can be operated by various organisations including:
- trunk road maintenance operators;
- local roads authorities;
- the police;
- and other interested parties.
Why introduce Variable Message Signs?
The Aims of VMS
The aim of using VMS is to provide drivers with mandatory and/or advisory information, at the roadside, relating to situations ahead or in the immediate vicinity. In relation to congestion it may be intended that VMS will assist drivers in selecting appropriate routes avoiding a traffic queue. VMS are considered useful in the event of an incident (e.g. road works, road accidents and other incidents), especially where alternative routes exist. To enhance management of the car traffic flow, VMS may be interfaced to traffic monitoring systems. These systems increase costs but also have potential benefits in providing drivers with more correct real-time information. VMS may be used to attempt to manage driver speed, either by informing drivers of variable speed limits depending on specific conditions at a given time (see e.g. Gudmundur et al. 2005) or in order to prompt speeding drivers to slow down (see Tay and de Barros 2007).
Potential Uses of VMS
Examples of the potential uses of VMS include:
- Advice on approaching lane closures (including tidal-flow systems) and appropriate speed limits by lane;
- General downstream hazards (slow/stationary traffic ahead, rescue vehicles on the road, oversize convoy, etc.);
- Information pertinent to route choice (roadworks & road closures, estimated delays, suggested alternative routes etc) either downstream on elsewhere on the neighbouring network;
- Information about public transport (typically in the vicinity of Park and Ride sites);
- Meteorological conditions (reduced visibility, slippery road, strong wind, etc);
- Environmental messages;
- Availability and location of parking spaces;
- Low bridge/ over-height/ over-weight vehicle warnings;
- Other generic dangers and safety advice.
Some of these are discussed in more detail below.
Lane Closures and Recommended Speed by Lane
VMS can be used to provide information about approaching lane closures and to show variable speed limits, either to enable drivers to slow down before reaching a downstream hazard (such as slow/stationary traffic) or to improve the general traffic flow by the use of variable speed limits.
Weather Information
VMS can be used to inform drivers of weather conditions such as fog, ice or snow. The information is normally only useful it relates to downstream conditions on the road ahead. However, they can also combine these with corresponding speed advice (see Gudmundur et al. 2007).
Parking Guidance Information
A parking guidance system needs four elements: a monitoring system; an organising system; a communication system and a display system. The VMS is the display. Monitoring of the car park needs to be done, the information monitored needs to be communicated and relayed/organised before it is ready to display. (See Traffic Advisory Leaflet ITS 4/03 for more information.)
Parking Guidance is covered in more detail elsewhere.
Variable Tolling
VMS can be used to display the price of variable tolls on roads or bridges or in areas of road user charging. Connecting the VMS to relevant traffic flow devices can reduce the need for human intervention.
Generic Dangers and Safety Messages
VMS is often used as a mechanism to provide general road safety advice, for example related to ‘drink driving’ or ‘take a break’.
Good Practice
Good VMS must convey useful and temporally correct information in a form that drivers can understand and assimilate quickly.
Distrust among drivers can arise if the messages displayed are not always correct. In particular, congested conditions at motorways junctions can quickly change thereby making a ‘congestion’ warning quickly out of date. Cooper and Mitchell (2002) showed that incorrect responses in navigating were greater where VMS displayed messages contradicted the other signs around them. This is due to the confusion that arises when drivers see a static advance direction sign displaying different information to that shown on a Variable Message Sign. In order to help drivers decide which information to trust the VMS may need to qualify what it displays; for example ‘Delay on M8 going west = 1 hour. Take A89 to avoid’ rather than just ‘Take A89 West’.
Demand impacts
The benefits of the signs in general are difficult to measure and little firm evidence exists on demand impacts exist. VMS are often used to inform drivers of congestion, incidents ahead and unexpected delays and can as such reduce drivers’ stress. Use of VMS is therefore not likely to reduce the demand for the road network. VMS are normally designed to aid car drivers using the network and make their journeys less stressful, shorter, safer and easier. Due to costs, VMS are normally only used where the information can be seen by many drivers, making them more economically viable on congested trunk roads where alternative routes are available. On the other hand, no firm evidence that VMS increase demand for car trips exists either. It is obvious that impact on demand depends on the type of signs installed and the information provided. Signs can be particularly beneficial for demand management where drivers can be informed of alternative routes or park and ride sites to avoid further delays, but this may require the VMS to be an integral part of a wider and more costly traffic monitoring system (including parking availability at Park and Ride site).
Application of parking guidance and information systems (PGI) can reduce search traffic where parking demand outstrips local supply by directing drivers to alternative sites. In city centres providing better information about parking available on route can be much appreciated by car drivers and reduce travel time significantly at peak times. At the same time these systems may reduce the competitiveness of public transport by eliminating the apprehension and stress some car owners can anticipate for a trip to a city centre, making them use public transport instead. See Parking Guidance Systems for more information.
VMS is likely to be more effective in handling demand if the messages are available to the public before they begin their journey. In New Jersey there is a direct link from the VMS sign to a page on the New Jersey Turnpike Authority website so those with internet access can see whether there are any roadworks or delays on the route they plan to take. In this scheme, the revenue generated from the tolls will pay for the VMS.
VMS may be used to display the roadside air quality at various points across a city, supplemented with public information displaying air quality targets. A benefit of such a message is that those that drive the most are the most exposed to the message. However, it is suggested here that such information has no direct impact on car usage, unless the information is more specific and provides information on travel alternatives, such as public transport route options and travel times.
The table below shows how VMS can affect the vehicle kilometres travelled by car.
| Responses and situations | ||
| Response | Reduction in road traffic | Expected in situations |
| Roadside VMS are unlikely to have any significant impact on vehicle kilometres by changing departure time. | ||
| / | Where alternative car routes can be used when given better real-time information to avoid incident or congestion. This will normally increase vehicle kilometres compared to the normal route unless drivers are directed to Park and Ride sites. | |
| Where drivers can find suitable parking by providing better real-time information. However, impact on vehicle kilometres unlikely to be more than slight. | ||
| Where providing better real-time information may attract additional car trips, e.g. improved real-time parking information. | ||
| Where reducing unreliability of car travel by reducing congestion and improving travel comfort by providing better car travel real-time information. | ||
| VMS are unlikely to have any significant impact on vehicle kilometres by affecting car ownership. | ||
| Where VMS improve conditions and travel time for long-distance car commuting this may induce people to move further away from their work place, if moving for other reasons. | ||
| = Weakest possible response | = Strongest possible positive response | ||
| = Weakest possible negative response | = Strongest possible negative response | ||
| = No response | |||
Short and long run demand responses
There will be no significant change in demand response of VMS as time goes on unless the technology of VMS is improved to provide more beneficial and effective information.
Impact on vehicle kilometres travelled will be largely dependent on type of VMS installed and the design of the integral Intelligent Transport System. Increased positive impact on vehicle kilometres of route changes can be expected if successively improved travel time information can be provided at more sites concerning Park and Ride (e.g. availability of parking, costs, route frequency, next suitable departure).
| Demand responses | |||||
| Response | - | 1st year | 2-4 years | 5 years | 10+ years |
| - | |||||
| Park and Ride information | / | / | / | / | |
| Change job location | |||||
| Where providing better real-time information may attract additional car trips, e.g. improved real-time parking information. | |||||
| Where reducing unreliability of car travel by reducing congestion and improving travel comfort by providing better car travel real-time information. | |||||
| Car ownership | |||||
| Move house | |||||
| = Weakest possible response | = Strongest possible positive response | ||
| = Weakest possible negative response | = Strongest possible negative response | ||
| = No response | |||
Supply impacts
There will physically be no increase in the supply of road space by VMS, but providing effective information may make more-efficient use of existing road network capacity where alternative routes with peak time capacity exists.
Financing requirements
The costs of VMS are made up of purchase, operating and maintenance. The prices of VMS depend on the types of technology and vary significantly depending of type of sign and the appropriate data and sensors required to compute an appropriate message to drivers. Comparatively the cost of a VMS will be significant greater than the cost of a regular sign giving a single message, but generally they also bring additional functionality. In some places the cost of this will be less than the cost of the time people waste for example if going onto a closed section of road. There might therefore be scope for some private investment.
Expected impact on key policy objectives
Signs have different potential benefits depending on the type of message they are designed for. VMS are often used to inform drivers of congestion, incidents ahead and unexpected delays and can as such reduce drivers' stress. Signs may be beneficial where drivers can be informed of alternative routes or park and ride sites to avoid further delays, but this may require the VMS to be an integral part of a wider and more costly traffic monitoring system.
| Contribution to objectives | ||
Objective |
Scale of contribution |
Comment |
| Great uncertainties of outcome. Rating represents low estimate. Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. Main contributions likely to be by giving drivers real-time information on alternative routes and improved information on likely arrival time. | ||
| No significant impact as roadside VMS normally concerns information about main road network conditions, delays and information concerning car drivers’ safety. Systems that target speeding in urban areas are beneficial. Incident information systems applied adjacent to residential areas may induce rat running, but no evidence of this exists yet. | ||
| No significant impact known of mainstream systems implemented up to date. VMS providing improved information on Park and Ride likely to have some environmental benefits but may also induce long-distance commuting. Parking Guidance Systems may reduce search traffic, see Parking Guidance Systems. |
||
| Indirect negative impact by aiming public resources towards improvement of car drivers’ comfort. | ||
| Great uncertainties of outcome. Rating represents low estimate. Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. Some types of VMS are expected to have an impact on speeding in urban areas. VMS warning of stationary traffic ahead are more likely to have a significant impact on motorways where speeds are higher than in urban areas and where signs are more easily located to suitable places. | ||
| / | Evidence on relationships between any travel time savings and economic growth are uncertain and contested (see e.g. Banister 2012). VMS perceived as beneficial by high-income road users. Investments may contribute to technological evolutions and new high-tech businesses. | |
| / | Significant public investments needed for installation, operation and maintenance. Some scope for private investments. If VMS signs effectively prompt speed reductions then there may be financial benefits in reduced spending on acute medical services. | |
| = Weakest possible positive contribution | = Strongest possible positive contribution | ||
| = Weakest possible negative contribution | = Strongest possible negative contribution | ||
| = No contribution | |||
Expected impact on problems
| Contribution to alleviation of key problems | ||
Problem |
Scale of contribution |
Comment |
Congestion |
By improved real-time traffic information where alternative routes and park and ride sites are available. Outcome uncertain as knowledge of suitable alternative routes and park and ride sites limited. By freeing up potentially productive time currently involved in unexpected delays and reduce stress by giving drivers improved information. | |
Community impacts |
Some reduction in visual intrusion by reducing the number of signs and amount of information in urban areas. | |
| Environmental damage | / | Possibly some reduction in carbon emissions if reduced congestion leads to more constant speeds, particularly if sufficient impact to remove stop start conditions. Re-routing likely to involve increase in vehicle kilometres. Demand impacts likely to be negative. Further possible benefits in reducing loss of green space if using existing road space more intensively and reduce pressure for new roads. |
| Poor accessibility for those without a car and those with mobility impairments | Indirect negative impact by aiming public resources towards improvement of car drivers’ comfort. | |
| Social and geographical disadvantage | No significant impact known. | |
| Accidents | Outcome uncertain. Rating represents low estimate. | |
| Poor economic growth | No significant impact known. Parking Guidance Systems may have impact, see Parking Guidance Systems. |
|
| = 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 |
May benefit from avoiding congestion by better real-time information on routes. | |
Small businesses |
May benefit from avoiding congestion by better real-time information on routes and providing real-time incident information. | |
High income car-users |
May benefit from avoiding congestion by better real-time information on routes and providing real-time incident information. | |
| People with a low income | People with a low income are unlikely to be car commuters. They are indirect losers as significant public funding is likely to be required to operate VMS. | |
People with poor access to public transport |
Indirect losers, significant public funding is likely to be required to install, operate and maintain VMS. | |
All existing public transport users |
Indirect losers, significant public funding is likely to be required to install, operate and maintain VMS. | |
People living adjacent to the area targeted |
No significant impacts known. | |
| Cyclists including children | If traffic speeds are reduced, and compensatory higher speeds outside the area of the VMS are avoided, then this may improve safety. | |
| People at higher risk of health problems exacerbated by poor air quality | If stop-start traffic is reduced then there might be benefits in some reduction of poor air quality. | |
People making high value, important journeys |
May benefit from avoiding congestion by better real-time information on routes. | |
| The average car user | Drivers want to see VMS used more. | |
| = Weakest possible benefit | = Strongest possible positive benefit | ||
| = Weakest possible negative benefit | = Strongest possible negative benefit | ||
| = Neither wins nor loses | |||
Barriers to implementation
The main barrier to implementation is cost. Some concerns may be also raised about visual intrusion of new signs. However, by reducing the number of stationary road signs it is here suggested that properly designed VMS can reduce negative aesthetic impacts. Long distance car commuters are likely to benefit the most, which may raise political issues of disproportionate advantaging of this group in the future.
| Scale of barriers | ||
| Barrier | Scale | Comment |
| Legal | There are usually no obvious legal barriers to the introduction of VMS. | |
| Finance | Costs of investment and operation. | |
| Governance | There are unlikely to be significant governance issues. | |
| Political acceptability | There are no obvious political barriers to the introduction of VMS. | |
| Public and stakeholder acceptability | There is some evidence of public support barriers to the introduction of VMS. | |
| Feasibility | Feasibility studies such as financial analysis are required to introduce VMS. VMS are generally less feasible in urban areas than on intercity routes. | |
| = Minimal barrier | = Most significant barrier |
There is evidence that VMS have an effect in warning drivers either of planning disruptions or incidents or conditions affecting the road ahead. Responses include slowing down and in some cases changing direction (Chatterjee et al. 2002). Studies have found that many drivers slow down in the presence of VMS, and while this speed reduction can be beneficial, in some cases it may be offset by compensatory behaviour of drivers once they have passed the vicinity of the signs, and in other cases speed reductions may be prompted by the VMS distracting the drivers, which can create a safety risk (Gudmundur et al., 2005; Erke et al. 2007).
There is some support among drivers for use of VMS signs to warn drivers of disruptive conditions and to encourage drivers to observe speed restrictions and limits (see Tay and de Barros 2007). Likewise Cooper and Mitchell's (2002) final report on the Safety and Effectiveness of the wider use of VMS found that:
- Drivers would like to see VMS signs used more;
- The effectiveness of VMS is dependent on the ability of drivers to assimilate and understand the information presented' information recall is greater when more key elements appear in a message although less of the complete message will be recalled; and
- In some circumstances drivers may not be able to absorb all the information presented to them and may become overloaded. They may not react to important information and/or their driving performance may suffer.
Chatterjee et al (1999) completed a study of the effectiveness of Variable Message Signs in London. The purpose of the signs is to notify motorists of planned events and current network problems. To guide investment and operational decisions an understanding is required of the impacts of VMS information. The study employed stated intention questionnaires to investigate the effect of different messages on route choice. Logistic regression models were developed to relate the probability of route diversion to driver, journey and message characteristics. The models indicated that the location of the incident and the message content are important factors influencing the probability of diversion. A survey of drivers' actual responses to a message activation showed that only one third of drivers saw the information presented to them and few of these drivers diverted, although they found the information useful.
Boyle and Mannering (1998) in their report titled, 'Impact of traveller advisory systems on driving speed: some new evidence' used a full sized fixed base driver simulator to collect data on drivers speed behaviour under four different advisory information conditions in-vehicle messages: in vehicle messages, out of vehicle messages, both in and out of vehicle messages and no messages at all. The findings of this study suggest an interesting phenomenon in that, while messages are significant in reducing speeds, drivers tend to compensate for this speed reduction by increasing speeds downstream when such adverse conditions do not exist. As a result the net safety effects of such message systems are ambiguous.
| Contribution to objectives | ||
| Objective | Scale of contribution | Comment |
| The case studies show that a significant number of drivers divert in response to a message advising this. | ||
| Not measured in the studies. | ||
| Not measured in the studies. | ||
| Not measured in the studies. | ||
| / | Drivers are shown to slow down in response to VMS, however the suggestion is that this can be due to distraction of the message. | |
| Not measured in the studies. | ||
| Not measured in the studies. | ||
| = Weakest possible positive contribution | = Strongest possible positive contribution | ||
| = Weakest possible negative contribution | = Strongest possible negative contribution | ||
| = No contribution | |||
| Contribution to objectives and problems | ||
| Objective | Scale of contribution | Comment |
| Great uncertainties of outcome. Rating represents low estimate. Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. Main contributions likely to be by giving drivers real-time information on alternative routes and improved information on likely arrival time. | ||
| No significant impact as roadside VMS normally concerns information about main road network conditions, delays and information concerning car drivers’ safety. Systems that target speeding in urban areas are beneficial. Incident information systems applied adjacent to residential areas may induce rat running, but no evidence of this exists yet. | ||
| No significant impact known of mainstream systems implemented up to date. VMS providing improved information on Park and Ride likely to have some environmental benefits but may also induce long-distance commuting. Parking Guidance Systems may reduce search traffic, see Parking Guidance Systems. |
||
| Indirect negative impact by aiming public resources towards improvement of car drivers’ comfort. | ||
| Great uncertainties of outcome. Rating represents low estimate. Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. Some types of VMS are expected to have an impact on speeding in urban areas. VMS warning of stationary traffic ahead are more likely to have a significant impact on motorways where speeds are higher than in urban areas and where signs are more easily located to suitable places. | ||
| / | Evidence on relationships between any travel time savings and economic growth are uncertain and contested (see e.g. Banister 2012). VMS perceived as beneficial by high-income road users. Investments may contribute to technological evolutions and new high-tech businesses. | |
| / | Significant public investments needed for installation, operation and maintenance. Some scope for private investments. If VMS signs effectively prompt speed reductions then there may be financial benefits in reduced spending on acute medical services. | |
| = 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 | Scale of contribution | Comment |
| Congestion | Great uncertainties of outcome. Rating represents low estimate. Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. Main contributions likely to be by giving drivers real-time information on alternative routes and give drivers improved information on likely arrival time. | |
| Community impacts | Some reduction in visual intrusion by reducing the number of signs and amount of information in urban areas. | |
| Environmental damage | Possibly some reduction in carbon emissions if reduced congestion leads to more constant speeds, particularly if sufficient impact to remove stop start conditions. Re-routing likely to involve increase in vehicle kilometres. Demand impacts likely to be negative. Further possible benefits in reducing loss of green space if using existing road space more intensively and reduce pressure for new roads. | |
| Poor accessibility | Indirect negative impact by aiming public resources towards improvement of car drivers’ comfort. | |
| Social and geographical disadvantage | Scale of contribution depends highly on impact on car traffic demand and which types and for what purposes VMS are implemented and design of system. | |
| Accidents | / | Some types of VMS are expected to have an impact on speeding in urban areas. VMS warning of stationary traffic ahead are more likely to have a significant impact on motorways where speeds are higher than in urban areas and where signs are more easily located to suitable places. |
| Poor economic growth | / | Evidence on relationships between any travel time savings and economic growth are uncertain and contested (see e.g. Banister 2012). VMS perceived as beneficial by high-income road users. Investments may contribute to technological evolutions and new high-tech businesses. |
| = Weakest possible positive contribution | = Strongest possible positive contribution | ||
| = Weakest possible negative contribution | = Strongest possible negative contribution | ||
| = No contribution | |||
Appropriate contexts
VMS can be used in all areas. However to justify their cost they would be best placed where a large number of people can view them or where they are seen to alleviate the risk of accidents or reduce congestion and driver stress.
| Appropriate area-types | ||
| Area type | Suitability | Comment |
| City centre | VMS will have to compete with other signage and will not get maximum effect in the city centre but could be used there if positioned sensibly. | |
| Dense inner suburb | Often little need and poor economical viability. | |
| Medium density outer suburb | On route between outer suburbs VMS could be useful to direct commuters. | |
| Less dense outer suburb | On route between outer suburbs VMS could be useful to direct commuters. | |
| District centre | Often little need and poor economical viability. | |
| Corridor | The ends of a corridor where drivers have a choice between routes is the ideal place for VMS. | |
| Small town | Often little need and less economical viability. | |
| Tourist town | VMS could be valuable in a tourist town to manage visitor traffic. | |
| = Least suitable area type | = Most suitable area type |
Adverse side-effects
The most significant adverse side-effects are potential collisions caused when people look at the signs for too long, instead of concentrating on their driving. A major side effect might be poor reliability of information given, or if drivers come to rely on the VMS and it breaks down. Visual intrusion of the signs may be an negative side-effect.
Banister, D. (2012) ‘Transport and economic development: reviewing the evidence. Transport Reviews 32 (1), pp. 1-2.
Boyle and Mannering (1998) Impact of traveller advisory systems on driving speed: some new evidence, found on the science direct website.
Bruneau, E (1994) Real Time Traffic Information: VMS and CARMINAT, Traffic Technology International, published by UK & International Press, ISSN 1356-9252.
Cooper B.R. and Mitchell J (2002) Safety and Effectiveness of the wider use of VMS - Final Report. TRL Report TRL526.
DfT (2003) Traffic Advisory Leaflet 1/03, Vehicle Activated Signs, March 2003, Traffic Advisory Unit, London.
DfT, (unknown). Real Time Information - Sources and Applications.
DfT (2003) Traffic Advisory leaflet ITS 4/03, Parking Guidance and information, by the Traffic Advisory Unit.
Chatterjee, K; Hounsell N.B., Firmin P.E. and Bonsall P.W. (2002) Driver Response to Variable Message Sign information in London, Transportation Research Part C: Emerging Technologies, 10 (2), 149–169.
Erke, A., Sagberg, F. and Hagman, R. (2007) Effects of route guidance variable message signs (VMS) on driver behaviour, Transportation Research Part F 10, 447–457
ERTICO (1998), www.ertico.com
Gudmundur, F. Ulfarsson, G. F., Shankar, V. N. and Vu, P.(2005) The effect of variable message and speed limit signs on mean speeds and speed deviations, International Journal of Vehicle Information and Communication Systems, (1) 1-2, 69-87.
IHT Institute of Highways and Transportation (1997) www.iht.org
Messmer, Papageorgiou and Mackenzie (1998) Automatic control of Variable Message Signs in the interurban Scottish Highway Network,
Ramo P and Kulmala R (unknown) Effects of Variable Message Signs for slippery road conditions on driving speed and headways, Technical Research Centre of Finland. Found on the science direct website.
Secretary of State for Scotland (1998), Scottish Transport White Paper, Travel Choices for Scotland, Chapter 4:-Scotlands Transport Action Plan web address: http://www.archive.official-documents.co.uk/document/cm40/4010/4010.htm
Silke, E (1994) Get the Message (Variable Message Signs), Surveyor, Pub by Hemming Group Ltd,
TA 83/99 Vol 9 Section 4, Part 6 is a guide to the use of Variable Message Signs for strategic Traffic Management on Trunk roads and Trunk Road Motorways
Tay, R., and de Barros, A. (2007) Public Perceptions of the Use of Dynamic Message Signs, Journal of Advanced Transportation, Vol. 42, No. 1, pp. 95-110