First principles assessmentWhy change parking regulations and access/egress arrangements
Vehicles parked on-street interact with moving traffic, and careful account needs to be taken of the requirements of moving traffic when designing the layout of regulations at any particular location. In some locations, parking is prohibited because of highway safety requirements. In others, parking is permitted at certain times when local access needs outweigh congestion and movement concerns. Kerbside regulations determine which activities (stopping, loading or parking) can take place, when and for how long.
On-street parking is the most convenient place for drivers to park as it provides door to door access, but this disrupts the general traffic and causes delays and congestion. In a typical street with approximately 60 parked cars per km, the average speed falls by 0.75 km/h with every ten additional parked vehicles.
In general, allowing on-street parking on a major arterial will decrease capacity and increase delays and accidents due to the physical occupation of the space, manoeuvres, pedestrians appearing in between vehicles and other activities associated with parking ( Hobbs , 1979). The capacity reduction factors for adjacent lanes resulting from parking manoeuvres are given in the Highway Capacity Manual (TRB, 2000). For example, on average 20 manoeuvres reduces capacity by 20% on one lane, 11% on two lanes and 7% on three lane roads.
Large off-street car parks can generate considerable blocking back of traffic waiting to enter the facility and delays where vehicles re-join the road system. There may be a particular problem if the surrounding streets are narrow or the entrance to the car park is near to a junction. Conventional management is often used to facilitate one-way access/egress and reduce the disruption on minor roads. However, where the car park is located adjacent to a major arterial with fast-moving traffic, there may be benefits to providing storage lanes that would allow vehicles to enter/leave at lower speed to improve safety and reduce the disruption to passing traffic (Hobbs, 1979; O’Flaherty, 1996).Demand impacts
Several empirical studies and models have shown that the availability of parking is an important influence on travel behaviour and hence the volume of traffic attracted to an area. Reducing the number of on/off street parking spaces may be more effective at encouraging drivers to use a different mode (or change destinations) than other policy measures.
Feeney (1989) suggests that this would have five main consequences on drivers:
Such area-wide schemes require careful planning; there is often public concerns over the details of the restrictions and the aesthetic impact of signs and road markings, and problems may arise if the displaced users continue to drive and park just outside the controlled area.
There is a general lack of research on the sensitivity of drivers to security issues but there is anecdotal evidence that shoppers choose to visit a particular centre on the basis of the local parking arrangements. A study by MVA (1998) found that the type of parking available is an issue; surface car parks are more attractive than multi-storeys, which are associated with difficulties in manoeuvring and poor security.
The following responses and situations are likely to be expected when on-street parking is removed from places where it disrupts moving traffic and provided in the form of off-street parking with better access and egress arrangements.
Supply impacts will vary according to type of parking. A reduction in on-street parking will increase road capacity and average speeds, and hence reduce congestion and vehicle emissions. Changes in volume of off-street parking will not alter the supply of road space, but may allow a re-designation of the function of a particular street.
Local authorities are increasingly using the planning system to control the supply of off-street parking. Most areas now have maximum, rather than minimum, parking standards associated with new developments and developers can negotiate to secure adequate accessibility to sites by all modes, but stringent allocations can lead to parking pressures on surrounding roads.Financing requirements
Providing new or additional on-street parking will incur up-front planning costs associated with surveys, consultation with local residents and businesses, and scheme design. There will also be construction, signing and marking costs, and on-going maintenance and enforcement costs. In addition to this, any new off-street parking will have substantial land costs.
When time, price or occupant-related restrictions are applied to on/off street spaces, the financial commitment needed to operate these spaces can be substantial due to technological requirements. Where high technology is needed or desired for better enforcement and management of parking, the cost might exceed the income generated by parking controls (parking tickets and fines). Comparison of different parking location and type related costs for implementation, administration and technology examples can be found at VTI (2004) (http://www.vtpi.org/parking.xls).
Expected impact on key policy objectives
The following assessment of impacts on key policy objectives are made on the basis of parking location as there is insufficient evidence of the effects of changes in access/egress arrangements.
Expected impact on problems
Whilst reducing the provision of on/off-street parking can reduce congestion, it can also increase traffic and emissions as drivers spend longer searching for spaces.
Expected winners and losers
Defining winners and losers in respect to all possible impacts is difficult. However the beneficiaries will include businesses with high values of time, average car users and public transport users if the search traffic and egress time for parking is reduced or eliminated along arterial corridors.
Barriers to implementation
The most significant adverse side effect likely to result from new on-street parking is slowing down general traffic as it searches or manoeuvres for parking. Similarly, new off-street parking may generate more traffic and it is likely to cause queues at access points. This can cause congestion and be avoided when access points are designed on side roads rather than main arterials. When locating new car parks, banning on-street parking or closing down existing car parks, there will often be some opposition from local business and possibly residents. However, it should be possible to overcome this by involving these groups in parking policy development and communicating the benefits especially with past examples of success.
Other potential adverse side effects include equity and social exclusion problems if care is not taken when designing parking controls. Adequate provision must be made for those with important or urgent reasons for parking near to destinations. Additionally, supply controls should not stop people undertaking activities.
Text edited at the Institute for Transport Studies, University of Leeds, Leeds LS2 9JT