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)
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.