Speed Limits through Westfields Park

Limerick City Council have made a huge and successful effort at improving the quality of parks in Limerick over the last decade. The work on the walkways out to the University and through Westfields have added to and improved amenities that the entire city can enjoy. It is somewhat surprising then, that there are plans to increase the speed limit through Westfields Park. The Condell Road bisects one of the most important parks on the Northside of the city. As with any proposal that affects the city, the benefits of the proposal should be weighed against the costs of the proposal.

The benefits are fairly tangible, a driver will save circa one minute traversing the 2.5km of road through the park. This is on clear roads with no traffic. The costs are fairly intangible. The road will be less safe for cyclists and pedestrians and the park itself will be less pleasant. We can say for certain that there will be an increase in accidents. It has been shown in repeated studies that increasing speeds causes an increase in accidents. Based on work by Nilsson in Sweden, a change in average speed of 1 km/h will result in a change in accident numbers by 4% for a 50 km/h road.

Similarly in the UK, based on empirical studies by Taylor, where changes in accident numbers associated with a 1 km/h change in speed have been shown to vary between 1% and 4% for urban roads and 2.5% and 5.5% for rural roads, with the lower value reflecting good quality roads and the higher value poorer quality roads.

The science is clear then, increasing speeds increases the likelihood of accidents. While this unfortunate truth needs to be weighed up with any speed limit increase, it is conceivable that a benefit of an increased speed could be such as to justify the subsequent increase in accidents. Is the speed limit through the park such a circumstance?  Is a benefit of a minute per driver enough to justify the increased risk of accidents in a park used by cyclists and pedestrians.

To place this argument in context, it is useful to consider the impact of accidents at the various speed limits. The European Commission studies make it clear. “Pedestrians, cyclists and moped riders have a large risk of severe injury when colliding with a motor vehicle. The difference in mass is huge and the collision energy is mainly absorbed by the lighter ‘object’. In addition, pedestrians, cyclists and moped riders are completely unprotected: no iron framework, no seatbelts, and no airbags to absorb part of the energy. For a collision between a car and a pedestrian, the following relationship between speed and survival chance was established Ashton and Mackay (1979)”

Car Speed % fatally injured pedestrians
32 km/h 5
48 km/h 45
64 km/h 85

It is worth reflecting on the devastating impact a collision at 64 km per hour has on a vulnerable road user. It is fatal in 85% of incidents. Again, is this the risk that users of the park should be subject to? Even at the current 50km per hour, the consequences of an accident are stark, with a 45% fatality rate.

It is also important to note that driving is a skill where studies show people display a tendency to over-estimate their abilities. Drivers, as a general rule, are not accurate at self assessing their driving abilities. It is possible that many accidents don’t just occur because of bad driving, they occur because people over-estimate their ability which leads to complacency and bad driving.

These studies clearly highlight just how dangerous high speeds are to vulnerable road users. With that in mind, it is important to note that it is for these reasons we prohibit cycling on motorways, likewise, it is why we restrict speed limits in urban areas. While these points are obvious they don’t seem to be prevalent in the debate about the speed limit through the park. We need to have a serious conversation about how safe we want all users of Westfields Park to be, and if the benefits outweigh the risks.

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