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Speeding: Should dynamic speed limits be brought into the UK?

With London Mayor Sadiq Khan looking to impose a 20mph blanket speed limit across the capital, is it now time to look at dynamic speed limits across the whole of the UK?

The general consensus among many politicians, local authorities and pressure groups is that speed kills, sadly it is an uncomfortable truth.

According to government statistics there were 1,770 road deaths in the UK in 2018, with many of those deaths attributed to speed. 

Government data also reveals that 52 per cent of car drivers break the 30mph speed limit, whilst 46 per cent of motorists break the speed limit on motorways. In what seems to be a bit of an anomaly, only 10 per cent of drivers break the speed limit on single carriageway roads, according to data from the Department for Transport’s (DfT) Automatic Traffic Counters in 2018.

According to Auto Express, the latest statistics did not include a detailed analysis of 20mph zones. However, a study published by the DfT showed that in 2017, 86 per cent of cars broke the speed limit in 20mph zones, a figure which increased to 94 per cent in the early hours of the morning. 

A 20mph speed limit in side streets, roads which are major pedestrian thoroughfares and outside schools is understandable, but what would the impact be if there was a blanket 20mph speed limit across an entire city 24hrs a day? As the data shows, the law is being broken already and thus raises questions over whether this trend would simply continue. 

The nature of road usage differs throughout the day and night on major thoroughfares such as the Holloway Road in Islington, London. During the daytime period it is a road that can become extremely busy with cars, cycles and pedestrians, it has a 20mph limit attached to it. As the usage changes in the evening and night, that speed limit currently still remains the same. 

The fact that 94 per cent of motorists break the 20mph speed limit in the early hours of the morning certainly leads to questions about the fundamental imposition of 20mph speed limits on certain roads such as this. 

This therefore begs the question as to whether we should assess the feasibility of dynamic speed limits (DSL), speed limits which alter according to time, weather and terrain.

According to Science Direct, dynamic speed limit systems are increasingly being applied worldwide, they are typically applied on roads that are classified as motorways. 

The main objective of DSL is to improve traffic safety through reductions in speed variations within and across lanes, and between upstream and downstream flows. There is however no reason why this couldn't be applied to inner-city roads. The results of an evaluation of a DSL system on motorways in Flanders, Belgium, showed that the number of injury crashes decreased significantly, by around 18 per cent after the introduction of the system. A separate analysis for serious and fatal injury crashes revealed a decrease of 6 per cent.

Although this data only takes into account vehicle on vehicle incidents because the system was trialled on motorways, the question needs to be asked, should this now be trialled on roads across London and other UK cities, not just on motorways.

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