Evidence on performance

Thomson and Richardson (1998) investigated the effects of policies to provide short-stay spaces in the centre and long-term parking on the outskirts of town using a small hypothetical CBD network. They found that the changes led to a substantial reduction in searching time as well as a significant increase in walking as motorists parked in the outer (fringe) areas and walked to their destination. There was little impact on alternative modes as motorists traded off increased walking time for reduced searching.

However, Axhausen and Polak (1991) and Feeney (1989) argue the walk time to the final destination is a key factor in modal choice. Indeed, an EU study in Helsinki (Cost, 2001) reported that increasing the walking distance between parking space and destination to 400 metres would result in a 9% fall in car use.

The effects of varying parking charges and supply have been demonstrated in several studies including work by TRL (Dasgupta et al, 1994). This compared the effects of parking restrictions and improved public transport on car use in five English cities; Sheffield , Derby , Reading , Leeds and Bristol . Halving public transport fares was predicted to reduce car use by 1% to 2%, whilst doubling parking charges reduced car use by 20%. Halving the number of spaces led to a 30% reduction in car use and an associated 35% increase in speeds. This meant that city-wide vehicle kilometres would decrease by 3-5% and carbon dioxide equivalent emissions would fall by up to 5.5%, but there was a detrimental impact on economic activity as some shoppers chose an alternative destination.

A more recent study into local authorities' attitudes towards traffic congestion found that increasing parking charges did little to influence visitors' choice of destination or mode (Healy and Baker, 1998). The findings showed that in the two years prior to the study charges had risen in most of the 132 authorities interviewed, but 85% said that there had been no corresponding decline in the demand for parking spaces.

It may therefore be more effective to reduce the supply. The closure of a local car park in The Hague (Gantvoort, 1984) led to a 20% reduction in car use and, of those no longer taking the car, 80% converted to public transport and the remainder became car passengers. This mode change was found to be permanent in the majority of cases and only a few who were dissatisfied with public transport, returned to driving.

The introduction of Controlled Parking Zones, which prohibit ‘non-essential users’ such as commuters, to create space for residents, shoppers and short term business users, have also been successful in reducing car use. A residents’ parking permit scheme in Munich (Topp, 1991) reduced car trips to and in the area from 44% to 32% and increased the public transport market share from 40% to 47%.

In contrast, a number of studies (Gantvoort, 1984; Abbott, 1995; Topp, 1993; Kolbenstvedt et al., 2000; Allen, 1993) have found that reducing or relocating parking provision is likely to increase the amount of time spent searching for a space, which may have adverse impacts on congestion (OECD, 1980). Application of [hyperlink] parking guidance and information systems (PGI) can reduce this generated traffic and providing better access and egress arrangements in combination with PGI technologies can reduce search times and traffic queues

There was a 14% average speed increased on Paris’ ‘Axes Rouges’ and 15% reduction in journey times on London ’s Red Routes after the removal of on street parking (Abbott, 1995). Theoretically, this will improve safety due to less obstruction to general traffic, however, it may also increase safety concerns and severance effects because of increased speed. Therefore the released road space should be managed with care; reallocation to cyclists and pedestrians can improve the quality of street space and enhance the attractiveness of the area.

In addition to the traffic-related outcomes discussed earlier, m odelling studies (Abbott, 1995; Dasgupta, 1994) showed that reducing city centre parking provision can result in environmental benefits. However, Dasgupta et al (1994) found that emission levels could increase in other parts of the city so that the overall effect was a small net reduction.