First principles assessment
Why introduce parking guidance and information systems?
In general, PGI systems aim to encourage a more efficient use of the parking stock, to reduce queuing at car parks and parking search times (Polak, et al.,1990), and consequently to cut search traffic.
Problems generated by the lack of parking spaces in predominantly, highly populated areas are manifesting themselves as increased traffic congestion and longer travel times. These in turn lead to a lower quality of life and a lower level of accessibility for citizens (Verhoef et al., 1995; Miles et al, 1998; Ison and Wall, 2002). Searching for parking spaces may be responsible for as much as 30% of the traffic on main urban roads (Allen, 1993) and time spent searching for a parking place can often reach up to 40% of the total travel time (Axhausen, 1994).
The use of PGI systems can assist drivers to improve network efficiency and accessibility by reducing time wasted searching or queuing at car park entrances. This in turn reduces congestion on the road network near the controlled car parks, benefiting other traffic (DfT, 2003). Non-quantifiable benefits include an improved public image of car park management, and reduction in driver frustration. Based on various studies (Gercans, 1984; Allen, 1993; Axhausen et al.,1994; Polak, et al.,1990; DfT,2003 ).
Benefits from a PGI system will be greatest when the demand for off-street parking is approximately equal to supply. If there is an excess demand for off-street spaces, PGI is expected to have little impact on problems caused. This is because the signs continuously would show ‘no space’. Also, if demand is sufficiently less than supply and spaces are easy to find, the system provides little benefit.
It is assumed that if drivers access parking information before they start their journeys, and if car parks are full, they can choose not to use their cars; go to the nearest available car park; or change their final destination. However t here is also a potential danger that by helping the motorist, they reduce the probability of drivers using an alternative more sustainable mode (DfT, 2003).
There is however some problem in getting drivers to make use of such systems. Axhausen et al (1994) found that drivers tended to adopt their own strategy and only turn to the parking guidance when this failed. Other studies show that drivers take limited notice of the parking guidance systems and then for certain types of information. Attitudinal and stated preference studies by Allen (1993) and other studies reviewed by Thompson and Bonsall (1997) bear this out.
Improved utilization of off-street long stay parking may improve the accessibility of short stay on-street parking areas. Reduced search traffic and shorter journey times will release some capacity that will improve the speeds that were originally lower around the car parks.
The cost for PGI varies according to the equipment, interface between the PGI and the parking sites and the communication system that will be used for the system. The exact costs of a PGI system depend on the vendor selected to provide the equipment, the interface method between the PGS and the car parks, and the communication system. Cost estimate for a PGI with 24 dynamic message signs in San Jose (USA) suggests the total cost would be $4.1 million, of which nearly $3 million is design and equipment cost (Spencer, 2004).
Studies suggest that the benefits of such systems can exceed the cost. A cost-benefit calculation made for SouthamptonPGI suggested that the PGI signs were economically viable (with an economic rate of return of 91%) and over a five year period the benefits outweighed the cost of installation and maintenance (Converge-D3.3.1, 2000). It found that annual reductions in vehicle operating costs and annual increases in revenue for the public transport operator exceeded the annual operating costs of PGI, with a benefit-cost ratio of 1.85 (Kempter et al. 1995).
Expected impact on key policy objectives
Parking guidance and management can improve network efficiency significantly, and environment and accessibility at some degree. Improved parking information from PGI systems can raise the public’s image of the area, which can lead to improved revenue generation within that area. It can lead to safer driving behaviour, as drivers are guided straight to an available space (UTMC, 05a Final Report Page 47). The efficiency and accessibility benefits from reduced searching may be associated with some reductions in environmental intrusion and accidents, but these will depend on the local circumstances.
Parking guidance systems can lead to a non-trivial reduction in the vehicle emissions under extreme conditions of good guidance and drivers who do not know where there are likely to be vacant parking spaces.
The emissions reductions depend on the level of demand for public parking places in relation to the supply. As the difficulty of finding a place increases, measured by the unaided search time or distance, then the benefits increase.
Emission reductions through benefits to would-be on-street parkers who fail to find an on-street place may take place. This could be a significant factor under circumstances where demand for on-street places is high.
Typical benefits are 2% reductions in emissions of CO and HC and 1% in emissions of NO X and PM 10S. Although larger benefits are possible under favourable conditions. It should be noted that these benefits may decrease as on-street parking places increase because drivers take one of these rather than travel to another off-street public car park (Thompson, R G 2001). In summary, the limited information so far available suggests that parking guidance systems and media information can contribute to the reduction of emissions by decreasing search times, particularly under congested conditions.
Expected impact on problems
Provision of parking information is expected to shorten the time spent on finding a parking space and waiting before parking a car, reduce irritation associated with it and lead to efficient and increased use of parking facilities. Reductions in on-street parking and cars driving around searching for spaces are expected to make road traffic smoother and improve the environment. Making parking facilities within the area easier to use is expected to reduce concerns about travelling to the applicable district by car and contribute to the revitalization of the region such as by improving the image of the area. The evidence from Southampton (Converge-D3.3.1, 2000) and Frankfurt (Axhausen et al., 1994) indicates that parking guidance information reduces the average time spent parking at times when there is a large demand for parking.
Expected winners and losers
Barriers to implementation
There are no serious barriers to implementation, as shown below.
Text edited at the Institute for Transport Studies, University of Leeds, Leeds LS2 9JT