The impact of a motorway extension in Glasgow on road traffic accidents

Funded by the NIHR PHR Programme

A new study published by Dr Jon Olsen at CRESH and colleagues at CEDAR in the Journal of Epidemiology and Community Health evaluated the impact of the 5-mile M74 motorway extension on road accidents that resulted in a casualty. The study found that it had no impact on the already decreasing trend of road accidents in the area.

The 5-mile M74 extension opened in June 2011 in the south of Glasgow, following a three year construction period. The new motorway, which is mainly raised above existing roads and dwellings, travels through relatively poor neighbourhoods of the city.

We found that the motorway extension had no impact on the already decreasing trend of road accidents in the local area and wider city region, either during construction or following its opening. Our results also showed that the motorway extension did not increase the number of road accidents either.

The open access version of the paper can be found here. The study formed part of a larger NIHR PHR programme funded evaluation of the new motorway which includes assessment of impacts on active travel, physical activity and wellbeing. The project is due to report in 2017.

An infographic describing road accidents in Glasgow can be accessed here.

M74 motorway


The environmental and health impacts of motorised transport and its infrastructure are well known. While in many developed nations the number of road accidents is decreasing, they remain a significant public health issue. During 2014 alone there were 1775 deaths on UK roads and a further 1.3 million worldwide. Recent guidance, such as that published by the UK National Institute for Health and Care Excellence, recommends that new transport infrastructure should prioritise travel involving physical activity. Yet, the dominance of motorised transport for most of our journeys means that transport developments which prioritise pedestrians and cyclists in UK urban areas are still relatively rare.

The M74 extension was controversial, with strong views both for and against its construction, but many of the arguments lacked a convincing evidence base. The then Scottish Government considered these arguments, published an environmental impact statement, and went ahead with construction.


The aims of our study were:

  • To evaluate the impact of the M74 extension on road accidents during construction and following its opening.
  • To describe recent changes in the distribution of casualties between types of road user (pedestrian, driver or rider, and passenger) and assess whether the M74 extension had any impact on these numbers.

Key findings and implications

  • There was a steep reduction in the annual number of road accidents in Glasgow, from 5901 in 1997 to 2914 in 2014.
  • Reductions were seen in all areas of the city, and for all types of road user.
  • We found no evidence of any additional impact either way of the motorway extension on the already decreasing trend in road accidents in the local area or the wider city region, either during construction or following its opening.
  • Our results suggest that policy makers cannot necessarily appeal to a likely reduction in road traffic accidents in justifying the construction of new urban motorway infrastructure.
  • It is possible that the M74 extension may have contributed to changing the spatio-temporal distribution of road accidents – for example, by shifting the burden of accidents into or out of poorer neighbourhoods. This will be examined in future research.


We used data from the UK Department of Transport about all road accidents for the period 1997 to 2014 that resulted in a casualty and were reported to the Police. We looked at all accidents occurring within each of three pre-defined study areas in Glasgow: an area that contained the M74 extension, an area containing an existing motorway (the M8), and an area with no motorway surrounding a suburban railway line in the north of the city). We conducted an interrupted time series analysis to examine whether the new motorway altered the long-term trend in monthly accident numbers.

 By Dr Jon Olsen

This article presents independent research funded by the National Institute for Health Research (NIHR). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.

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