Congestion Charging
Background
It is widely accepted in economic theory that the welfare of society is maximised if all economic agents are faced with prices that reflect the true internal and external costs of their resource utilisation. The principle of marginal cost pricing states that a social optimum occurs where the social benefit of the last marginal unit of any product or service equals the social cost of producing it. This concept is particularly relevant within urban road transport, where there are significant social costs associated with congestion which are external to the personal cost faced by the user who generates them (eg delays to other users in the system). Based on this reasoning, strong arguments have been put forward in support of road pricing as means of improving the efficiency of road transport, by controlling excess demand for road use, especially in the most heavily congested cities. However, the practical pricing mechanisms required to implement marginal cost pricing for urban road transport in reality are far from obvious.
What is Congestion Charging
The underlying concept of the Congestion Charging system is that, like marginal cost pricing for the external costs of congestion, charges would only be levied when delays occur. This can be achieved with advanced technology on-board a vehicle through an electronic IVU which debits value from an inserted smartcard only when a certain, pre-specified level of delay is encountered. Linking a clock and an odometer, in similar fashion to a taxi meter, allows the IVU to perform continuous calculations of the time taken to travel a certain unit of distance. By specifying a critical time value for travelling a certain unit of distance, it is then possible to set a congestion threshold, above which a charge would be levied.
Simulation of congestion charging
Reliability affects the amount of time passengers must wait at a transit stop for a transit vehicle to arrive, as well as the consistency of a passenger’s arrival time at a destination from day to day. Reliability encompasses both on-time performance, as well as the regularity of headways between successive transit vehicles. The aims of this study are: The network used in this section considers the North Area of Leeds, including the above Otley Road Corridor (Figure 5 insert). It consists three main radial routes (Kirkstall Road, Otley Road and Meanwood Road) from the northern ring road to the city centre, and many minor orbital roads that give a significant amount of route choice. The network has 175 nodes, 70 zones and 1748 routes used by a peak-hour demand of 23,000 trips, about 25% of the total morning peak demand for the city.
The north Leeds network.
The DRACULA model was used to analyse features of the threshold approach in Congestion Charging, in particular that:
- Charges would be expected to vary by route rather than by link
- Charges may vary significantly over a relative short timescale, related to quite small variations in networks conditions close to the threshold level
- The definition of the threshold would need to include a margin of error, charging for less than 100% of delayed time, to ensure that vehicles would not be penalised for being courteous and obeying traffic regulations in un-congested conditions
- There may be significant variations in charges on a day-to-day basis
Video of Dracula model.
Results of study
Spatial distribution of link delays and Congestion Metering charges.
- Congestion charging charges may vary significantly over time, thus difficult to predict charge levels
- Locations of congestion charging charges and delays may differ
- Results have implications to congestion charging as approx. to marginal costs and incentive to drivers towards more efficient driving behaviour