1. Centre for Transport Aberdeen 12- 11-08 An Investigation of impacts VMS on safety on Scottish Trunk Roads Wafaa Saleh TRi, Napier University, Edinburgh

2. Centre for Transport Aberdeen 12- 11-08 Contents 1.Introduction to VMS 2.Literature 3.Research gaps 4.Main research objectives 5.Research methodology 6.Source of data 7.Modelling estimation results – accident rates and accident severity 8.Discussions 9.Conclusions and Further Works

3. Centre for Transport Aberdeen 12- 11-08 Introduction to VMS To inform drivers of dangers ahead (e.g., adverse weather, accidents) To inform motorists of congestion, roadwork, or speed limits ahead, etc.

4. Centre for Transport Aberdeen 12- 11-08 Wafaa SALEH Craig WALKER & Chih-Wei PAI An Investigation of the impacts of

5. Centre for Transport Aberdeen 12- 11-08 Literature VMS for Speed reduction information and unexpected events - a 30% - 48% reduction of accident rates -effective in diverting motorists - a reduction in speed in upstream but an increase downstream

6. Centre for Transport Aberdeen 12- 11-08 Research Gap Results re accidents reductions are not conclusive Overall reduction in accidents do not mean resulting from VMS The effect of VMS on accident severity? The interaction effects of other factors with VMS?

7. Centre for Transport Aberdeen 12- 11-08 Therefore… A review of the literature suggests that while consistent conclusions have been suggesting that a reduction of speed was observed as a result of a sign that urges a reduced speed, there was a concern for an increase in speed downstream The net safety effects of such message systems were rather inconclusive in the literature

8. Centre for Transport Aberdeen 12- 11-08 Research objectives To investigate the impacts of VMS on accident rates and severity on Scottish trunk roads - A before-and-after analysis of accidents at 14 selected VMS sites in Central and North-East Scotland is presented.

9. Centre for Transport Aberdeen 12- 11-08 Data sources The number and locations of accidents at 14 selected VMS sites -NADICS website -Glasgow ITS department of the Faber Maunsell Engineering Consultancy Other factors that affect accident rates and severity: - The UK Stats19 accident injury database

10. Centre for Transport Aberdeen 12- 11-08 Wafaa SALEH Craig WALKER & Chih-Wei PAI An Investigation of the impacts of

11. Centre for Transport Aberdeen 12- 11-08 Data sources The number and locations of accidents at 14 selected VMS sites -NADICS website -Glasgow ITS department of the Faber Maunsell Engineering Consultancy Other factors that affect accident rates and severity: - The UK Stats19 accident injury database

12. Centre for Transport Aberdeen 12- 11-08

15. Analysis of accident rates Accident rates

16. Centre for Transport Aberdeen 12- 11-08 Effect of VMS on accident rate Effectiveness of VMS

17. Centre for Transport Aberdeen 12- 11-08 Overall accident rate (k) 2000-2006

18. Centre for Transport Aberdeen 12- 11-08 ROADVMS CODE X ACCIDENTS Q (AV.)L (KM)T (YEAR)K (ACCS/10 8 VEH-KM) SE (ACCS/10 8 VEH-KM) M9N3617515276.702.74 W2518006275.432.43 W3218857272.081.47 W4218088272.161.53 A720M7930401275.791.93 M8O369310662743.475.23 O61026476277.392.34 O725442275.382.04 V21026377277.422.35 O918250362714.073.32 V11336582276.951.93 A90G111122852717.525.28 G2410871277.203.60 D614127562721.485.74

19. Centre for Transport Aberdeen 12- 11-08 ROADVMS CODE ACCIDENT DATA (BEFORE)ACCIDENT DATA (AFTER) K BEFORE VMS (ACCS/100 M VEH- KMS) K AFTER VMS (ACCS/100 M VEH- KMS) BEFORE AND AFTER % DIFFERENC E X Accident s Q Averag e L (km) T (yr) X Accident s Q Averag e L (km) T (yr) M9N3 4171392521845522 6.397.4216.09% W2 4165712512159222 6.613.17-52.03% W3 2177642502159022 3.080.00-100.00% W4 2172062401926323 3.980.00-100.00% A720M7 4300422453088123 4.567.3962.14% M8O3 463043624233190523 51.7632.92-36.40% Accidents data before and after installing VMS

20. Centre for Transport Aberdeen 12- 11-08 Percentage effectiveness of VMS including the control zone information

21. Centre for Transport Aberdeen 12- 11-08 Percentage effectiveness of VMS 95% CI VMS ө ESTIMATE % VMS EFFECT 95% CI EFFECT RANGE N31.16089616.09%0.2136.338-78.74%533.82% W20.479663-52.03%0.0544.292-94.64%329.17% W30-100.00%0.000 W40-100.00%0.000 M71.0377033.77%0.2793.864-72.13%286.44% O30.635975-36.40%0.3861.049-61.45%4.91% O61.48940648.94%0.4205.278-57.97%427.80% O1.63774663.77%0.3677.318-63.35%631.77% V20.304464-69.55%0.0791.177-92.13%17.74% O91.82727782.73%0.7214.630-27.88%362.99% V10.577838-42.22%0.1941.719-80.58%71.94%

22. Centre for Transport Aberdeen 12- 11-08 Chi-squared results for the 14 VMS

23. Centre for Transport Aberdeen 12- 11-08 Analysis of accident severity Two binary logit models (KSI vs non KSI accident) were estimated -the overall binary logit model -the binary logit model conditioned on the absence of VMS (interaction effects of absence of VMS with other variables)

24. The overall binary logit model

25. Interaction binary logit model

26. Centre for Transport Aberdeen 12- 11-08 Summary and conclusions Installation of VMS resulted in all reduction of accident rate (16.9%). However, when the control sites were taken into account, installation of VMS might have resulted in an increase in accident rates on the roads upon which they were placed. The presence of VMS reduced accident severity at the considered sites.

27. Centre for Transport Aberdeen 12- 11-08 Further work Analysis of accident rates and severity with larger data and wider area coverage Taking into account other impacts such as national trends of accidents rates and impacts of speed reductions, etc.