Effects of new urban motorway infrastructure on road traffic accidents in the local area: a retrospective longitudinal study in Scotland.
The M74 motorway extension, Glasgow, opened in June 2011. One justification for construction was an expectation that it would reduce road traffic accidents (RTAs) on local non-motorway roads. This study evaluated the impact of the extension on the number of RTAs, stratifying by accident severity.



Data for the period 1997-2014 were extracted from a UK database of reported RTAs involving a personal injury. RTA severity was defined by the level of injury: minor, severe or fatal. RTAs were assigned to (1) the local area surrounding the motorway extension, (2) a comparator area surrounding an existing motorway or (3) a control area elsewhere in the conurbation. Interrupted time-series regression with autoregressive integrated moving average (ARIMA) errors was used to determine longitudinal between-area differences in change in the number of RTAs, which might indicate an intervention effect.



Glasgow and surrounding local authorities saw a 50.6% reduction in annual RTAs (n: 5901 to 2914) between 1997 and 2014. In the intervention area, the number of recorded RTAs decreased by 50.7% (n: 758 to 374), and that of fatal/severe RTAs by 57.4% (n: 129 to 55), with similar reductions in the comparator/control areas. The interrupted time-series analysis showed no significant between-area differences in temporal trends. The reduction of pedestrian casualties was attenuated in the intervention area relative to Glasgow and surrounding authorities.



Reduction in RTAs was not associated with the motorway extension. Our findings suggest that in planning future investment, it should not be taken for granted that new road infrastructure alone will reduce RTAs in local areas. Urbanisation is proceeding rapidly worldwide, and evidence of infrastructure changes is lacking; this novel study provides important findings for future developments.
Centre for Research on Environment, Society and Health, Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK.
Jonathan R
JR
Olsen
Centre for Research on Environment, Society and Health, Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK.
Richard
R
Mitchell
Institute of Health and Wellbeing, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
Daniel F
DF
Mackay
Department of Social Policy and Intervention, University of Oxford, Oxford, Oxfordshire, UK.
David K
DK
Humphreys
MRC Epidemiology Unit, UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge, Cambridgeshire, UK.
David
D
Ogilvie
D000063:Accidents, Traffic / Q000401:mortality / Q000706:statistics & numerical data*; D002947:Cities; D004779:Environment Design; D005260:Female; D006801:Humans; D015601:Injury Severity Score; D065186:Interrupted Time Series Analysis; D008137:Longitudinal Studies; D008297:Male; D012189:Retrospective Studies; D012606:Scotland
ACCIDENTS; Environmental epidemiology; INJURY; Outcome Research Evaluation; TRAFFIC