ÓRGANOS ADMINISTRATIVOS, DE GESTIÓN Y DE

Hargreaves (1997) summarised the benefits of traffic calming including that these traffic management methods could reduce the traffic using a residential road as drivers seek routes without traffic calming. Traffic calming measures can reduce the speed of vehicles and this has corresponding improvements in safety and a reduction in noise from high-speed vehicles. Another advantage is that the number of heavy goods vehicles using the residential street could be halved. The traffic calming measures could be designed and constructed to the same level as the footpaths thus creating a safe crossing area. The disadvantages of traffic calming measures include emergency vehicles could take longer to travel along a calmed road and the journey would not be as comfortable as driving along a road with no humps.

Int Panis et al. (2006) carried out a study on traffic calming measures in Belgium, where whole districts were converted in 30km/hr zones, usually in residential areas. The aim of these measures was to improve road safety. These schemes were also promoted as improving the environment through lower fuel usage and reduced air pollution. Int Panis et al. (2006) investigated the correlation between reducing traffic speed and air pollutant emissions. Using real life urban driving cycles and the VeTESS tool to calculate emissions for specific types of modern cars, Int Panis et al. (2006) compared real life emissions with artificially modified driving cycles limiting the top speed to 30 km/h where appropriate and elongating the cycle to preserve the original cycle distance. The study concluded that with the exception of PM from diesel engines, the most common air pollutants did not change substantially due to a decrease in speed.

Research shows that traffic calming measures can be effective in reducing speed, accidents and noise and that the most effective traffic calming measure with respect to speed reduction is vertical changes to the carriageway. However, these measures are only effective if the speed humps or speed table are spaced sufficiently close together to make drivers slow down. Harvey (nd.:section 5) points out that a survey of 35 traffic calming schemes in the UK found that the average reduction in speeds was 16 km.hr. If these measures are designed correctly, with measures located within 60m of each other, then it is possible to see that 85 percentile travel at a speed of less than 30kph. These reductions in speeds have a positive impact on accident rates, with slower vehicles reducing both the accident rate and the severity of the accidents. According to Pharoah & Russell (1989) a study in Germany found that accidents

rates decreased from 6.2 per 100,000 of population to 2.3 per 100,000 in areas where traffic calming measures had been implemented. Harvey (nd.:section 5) also cites a study in Denmark which reviewed 600 traffic calming schemes in Denmark and found that these schemes had a 43% lower accident rate than untreated zones. Traffic calming measures can also lead to a reduction in noise, which is attributed to lower traffic volumes and speed. Pharoah & Russell (1989) suggest that traffic calming measures can also lead to a reduction in air pollutant emissions resulting from lower speeds but reduction levels were influenced by driving style. Harvey (nd.:section 5) cites a study in Germany which monitored vehicle emissions before and after the implementation of traffic calming and found that the traffic calming measures resulted in a decrease in Carbon Dioxide levels of 20% with a reduction of 10% in Hydrocarbons and 33% in Nitrogen Oxide.

In a Tyne and Wear study on bus lanes, which can be used as a means of traffic calming (Mulley et al, 2007), very few of the accidents in the study area were linked to the new priority measures on the traffic lanes. Contravention of the road traffic measures only occurred in 0.7% and 2.4% for different cases. However, a lower level of traffic was seen were it was postulated that it used different routes and cut through. There was uncertainty whether traffic journey times increased, with some increasing and some reducing although there were also other traffic changes at the time of the study which may have affected these results.

Car users are shown to dislike traffic calming measures in surveys, bus operators are shown to believe that any kind of priory system for buses was a good thing (Mulley et at, 2007), although cyclists and pedestrians are shown to generally have a more positive response to them. As they force traffic to move at a slower speed they are likely to reduce accidents and make the environment more pleasant for non-motorised transport and pedestrians. The lower speeds and potential requirement for vehicles to start and stop would result in higher traffic emissions, which would increase the influence of the cars on climate change, particularly from cold engines, when vehicles are on short journeys. The increased amount of stopping and starting could increase the noise level, although the overall lower speed would decrease the noise level so any assessment on noise levels would need to be considered more carefully on a case by case basis. As mentioned by Mulley et al (2007), as traffic calming measures could lead to traffic rerouting their journeys, it may just move the problem to another area rather than result in lower speeds and less accidents.

Hargreaves (1997) carried out a study into attitudes to traffic calming measures. The study involved asking residents of a residential area in Leeds to choose between three options, leaving the streets as existing without traffic calming measures, choosing round-topped road humps construction with tarmacadam or flat topped road humps constructed using block pavers. Respondents living on the primarily residential streets were asked to choose between three options. Respondents living in an area with mixed priority streets were given five options, the three previously mentioned plus an option for speed cushions, which are small tarmacadam humps that buses can straddle and small cars can avoid going over them. There respondents were also given an option of pinch points or chicane which is a localised narrowing of the roadway. All the devices were to be placed at 60m intervals and road humps were to be 100mm high. The study found that a significant number of residents on the mixed priority route were against traffic calming measures despite the higher volume of traffic and traffic speeds experienced along these roads. Residents in these areas justified their choice by stating that they had chosen to live in a mixed priority area specifically for easy road access and public transport routes, they had developed resilience to the impacts of high volumes of traffic and believed that these “through roads” were not suitable for traffic calming measures. On the mainly residential streets, the residents not in favour of traffic calming measures were strongly opposed to traffic calming schemes. The researchers concluded that people’s views on traffic management measures such as traffic calming is largely based on current personal concerns and circumstances at that time. Where residents were in favour of traffic calming, road safety was a priority, stating that traffic calming measures would ensure that traffic was diverted to more appropriate roads. Aesthetics of the speed humps were important to residential areas. In the mixed priority areas, there was opposition to the pinch points as it was believed that these would cause problems for drivers navigating the road and could cause problems for parking. Some respondents believed that the flat topped speed humps could be a safety hazard as pedestrians may believe that they had priority over road vehicles. Most of those polled who were in favour of traffic calming chose speed cushions as the preferred method, stating that other types of traffic calming measures were uncomfortable for drivers (Hargreaves 1997). Speed cushions are also considered the best solution along bus routes as they have less impact on the bus, do not substantially affect bus passenger comfort levels and reduce speeds (TfL 2005).