Demand management for road transport is one way of reducing congestion. This can involve relatively straightforward access control techniques or categorising vehicles (for example by their number plates) to restrict flows entering a given area. More intensive measures include charging for use of the road during congested periods, or the introduction of special high-occupancy vehicle (HOV) lanes.
There seems to be no fixed condition for the use of demand management. In most cities and regions that suffer from traffic congestion some method of demand management is undertaken. In general terms the severity and directness of the methods taken are proportional to the congestion problem that the area is facing.
Demand management covers all the measures that aim to limit the consequences of increased congestion and a decreasing level of service on a route. This is carried out through actions related to the local mobility policy, such as improving traffic distribution through time or encouraging users to modal transfer. Demand management is close to some traffic management actions that are mutually complementary. Operational tasks related to demand management will be integrated with a more global and multi-modal mobility policy with the road being part of it.
A number of strategies exist for reducing traffic demand by encouraging changes in traveller behaviour. Some examples are:
With the exception of the last, these programmes are implemented through marketing campaigns and do not require technology tools for the most part.
A more direct approach is through the use of pricing incentives, or disincentives. Increasingly electronic ticketing and electronic payment methods are utilised to pay for transport services and ITS technologies can be used to keep track of transactions, clients and other data useful for improving operations and providing customised services. (See Congestion Charging and Variable Pricing)
Examples are:
Major urban congestion charging schemes have been introduced in Singapore using Electronic Fee Collection (EFC) and in London (UK) using a variety payment methods and a permitted list, backed up by “smart” camera enforcement. (See Back Office Arrangements and Enforcement)
There are other methods of demand management, which may not directly involve the road authority, for example the promotion of park-and-ride, ride share schemes and public transport. (See Transportation Demand Management) Subsidies for these programs may also be helpful. Another method would be to increase the usability of public transport through common passes or smartcards. (See Passenger Fare Payment)
It can be argued that various urban renewal schemes or master plan development, such as the creation of work places closer to the residential area would be a part of an overall demand management policy. This would go far beyond the normal role of a road network operator and is not considered here.
One of the most frequently used measures of demand management is information provision. This could be information provision before the trip, or information provision on the trip. Users may look up the traffic information through various methods, such as the Internet, conventional media such as TV or radio, smartphones, VMS and on-board units. Based on the information, the user would make an individual judgement to take another route, thereby reducing the demand for a certain section of the network, or change to public transport (as in the case of park and ride systems), change the time of the trip, or not use the car at all for the trip. (See Pre-trip information)
Journey planning and travel information provision is available in most cities. This is a fairly simple method that can be implemented for a relatively low cost. It is not restrictive and it leaves the actual decision on whether and how to travel to the users themselves.
Implementation issues: Information provision itself does not present significant implementation problems, although there are issues to do with information coordination and collection, information processing and the dissemination method that need to be worked out. (See Travel Information Systems)
On-trip information provision does not necessarily decrease the total traffic demand. More likely, it will simply re-channel the demand into a different part of the network. Therefore, in cases where the entire network is congested or there are no alternative route or transportation methods, the effectiveness of this method will be limited.
Another problem associated with information provision is the undesirable flow of traffic that may occur as a result. In order to avoid the traffic congestion ahead, many drivers divert onto side roads creating through traffic in a residential district or a school zone, increasing the risk of accidents. In these cases there is a danger that information provision may create more problems than it would solve. Since this is hard to foresee, a careful monitoring of the traffic pattern after introduction is essential.
The technical development of electronic payment has made it possible to apply the concept of a road toll beyond the recovery of operational and infrastructure costs. Road pricing is a tool for traffic management, especially in urban areas that experience heavy traffic. The objective is to spread traffic throughout time in order to avoid saturation in a controlled area or on a toll motorway, bridge or tunnel. More efficient use of the transport system is achieved if people are persuaded either to change their time of travel away from peak periods, or shift from travelling by car to using an alternative travel mode. Often the money raised from road pricing is applied to the improvement of public transport. (See Congestion Charge)
Where there is an imbalance between supply and demand, the standard economic solution for any scarce resource is to let the market decide. The market would bid the price of that product up or down until the demand matches the supply and the market clears. Traffic congestion is evidence of an imbalance between the supply and demand for roadspace, and so controlling it through pricing is an obvious solution. Economists will assert that road pricing is an extremely sensible and rational measure for dealing with an excess of traffic demand. For toll roads, this would seem to be a textbook solution.
A road pricing system needs a tolling and payment system with back-office arrangements that have the capability to charge by distance, by type of vehicle and so that charge can be varied, up or down, to reflect conditions of time and place.This was impractical until the development of electronic payment systems and Electronic Toll Collection (ETC) in particular, since with a manual system it is difficult to implement a different price (toll) for a given time period. Electronic payment systems allow flexible charging, which can be on the basis of time, place and distance. (See Electronic Payment)
With ETC variable pricing is technically more straightforward but it is not adopted as widely as it could be. Generally there is hostility from road users whenever a road pricing scheme is proposed. The main argument against it concerns fairness and equity - a perception that road pricing only allows more wealthy people to use the road. It can achieve the goal of easing congestion by limiting the demand, but the impact on poor people is disproportionate. There are counter-arguments but the perceived inequlaity is an obstacle that is difficult to overcome politically. With some notable exceptions, politicians have been unwilling to take on this issue. Consequently, this method as a demand management measure is implemented in relatively few places around the world.
Whatever the aims of a road pricing policy, from an operational perspective it is necessary to minimise user inconvenience when using the payment system. Electronic payment methods can limit the discomfort and improve road safety and efficiency. (See Payment Technologies and Process)
Variable tolling is an example of road pricing that operates to spread traffic over time in order to avoid gridlock at times of peak demand or during heavy seasonal travel. Alternatively it can be used to generate more traffic by giving a discount on the usual toll when the volume of traffic is low.
The principle of variable tolling is to raise tolls during peak periods (“red” periods) and lower them during periods of lighter traffic (“green” periods). Implementation is based on publicity and information dissemination:
In the case of free-flow toll facilities, the toll level can be changed throughout the day, which requires real-time information to road users, informing them of the current toll rate through VMS.
Some precautions are required to:
Variable tolling can be cumbersome to manage (for example adaptation of toll equipment and the need for user information). Higher peak-period tolls are unpopular and are viewed as a hidden attempt to increase total revenue. Success is as dependent on user acceptance as on the technical relevance of the measures introduced. It essentially depends on three factors:
The application of this measure on toll-roads in France, showed a decrease in peak period traffic (average reduction of 10 percent) with no reduction in total demand or lasting diversion of traffic to parallel roads.
Variable tolling has become more common with the use of smartcards and electronic tags. As ETC is adopted more widely the integration of new ETC systems with older systems becomes a problem. As ETC systems are improved or upgraded, compatibility with the old units becomes an issue. This can be handled through good equipment standardisation, agreements between operators on evenue sharing and agreement on a consitent interface, for example on the classification of different vehicle types.
There is no certain way of reducing traffic demand - it is often a diverse and difficult issue. Various methods need to be combined in response to local requirements. Even in the simplest method of information provision, consultation with and coordination of the parties involved is essential, with careful monitoring of the effects of controls. This is particularly true for direct methods of demand management by means of access control.
A common method is to remove through traffic from a controlled zone by restricting entrance to that zone only to users who have an electronic pass, or through vehicle licence-plate recognition. (See Policing / Enforcement) This is typically done by signs that announce the restrictions and a gate or barrier at each entrance of the zone where the electronic pass or vehicle licence plate can be checked. Checking is sometimes done manually although there are ways to do this automatically through the use of ANPR and "permitted lists" (lists of authorised vehicles), or with on-board transponders as a basis for enforcement.
Entry restrictions are always politically difficult to implement, although perhaps not as difficult as road pricing. The issues commonly associated with this restriction are political, the cost of equipment or staff required to enforce the restriction and the numbers of users who seek exemption or try to evade the system. In the case of a High Occupancy Vehicle (HOV) lane, for example, there have been cases where people are paid to ride in the user’s vehicle. Also, the restriction of traffic may have negative effects on the area’s economy, which may be a source of criticism. The challenge always is to reduce vehicular traffic without limiting productive activities within the area.
Ramp metering is a method to restrict the entry of vehicles to a motorway from a selected on-ramp in order to maintain free-flow conditions on the main carriageway. The implementation is fairly easy, since the number of ramps is limited and they can be controlled by the network operator. Ramp metering and entry restriction are widely used in the USA, either based on the numbers of vehicles, or selectively (for example High Occupancy Vehicles (HOV) only). (See Highway Traffic Management)
Ramp metering is becoming increasingly common outside USA. Implementation issues are not large, although there can be resistance from some users. An issue which sometimes needs careful attention is the storage capacity of the ramps, since queuing which tails back onto surrounding main roads may cause congestion to spread and reduce the level of service on the arterial roads.
The purpose of mode transfer is to create conditions that foster greater use of public transport (modal shift) to counter increased traffic volumes and congestion during rush hours, or following a major capacity reduction over an extended period (with risk of major daily traffic jams over several months). Both situations can lead to an acute drop in road network service levels due to a lack of roadway capacity.
The measure is attractive:
Mode transfer incentives can also be used in response to other situations such as poor air quality and a forcast increase in air pollution.
The objective is to promote greater use of public transport in order to reduce the number of vehicles on the road. A common approach is the use of information to the user in real-time on public transport services and on the existence of multi-modal journey transfer points, such as "park-and-ride". (See Transportation Demand Management) This is done through journey planning websites, and in real-time with VMS or in-vehicle information devices (conventional broadcasting, RDS-TMC, route guidance systems). (See En-Route Information)
The anticipated problems (for example daily traffic jams, or lengthy delays) must be well-publicised in advance or braodcast in real-time through travel aid and user information measures (VMS or in-vehicle equipment, smart-phone text messages and social media).
Car pooling or use of public transportation can be encouraged by upgrading the service frequency and capacity, especially during rush hours.
This measure requires preparation involving all partners starting several months before the planned disruptions are scheduled. (See Traffic Management Plans) It is implemented in the following stages:
Publicity need to convincing and persuasive enough to overcome reluctance and rigidity in the response of road users. Success also depends on:
Different strategies are needed to achieve a mode transfer for freight. Integrating actions on freight management. This may be seen as a long-term measure within the road network operations strategy. particularly when the aim is to shift goods off the road amd onto other modes. (See Users and the Delivery Process)