2104数学建模美赛A 交通流 安全性 参考资料 交通量

2104数学建模美赛A 交通流 安全性 参考资料 交通量

ROAD ACCIDENTS AND TRAFFIC FLOWS:AN ECONOMETRIC INVESTIGATION

Andrew Dickerson, John Peirson and Roger Vickerman

April 1998

Abstract

This paper develops an empirical model of the relationship between roadtraffic accidents and traffic flows. The analysis focuses on the accidentexternality which is mainly determined by the difference between themarginal and average risks. The model is estimated using a new datasetwhich combines hourly London traffic count data from automated vehiclerecorders together with police records of road accidents. The accident-flowrelationship is seen to vary considerably between different road classes andgeographical areas. More importantly, even having controlled for these andother differences, the accident externality is shown to vary significantly withtraffic flows. In particular, while the accident externality is typically close tozero for low to moderate traffic flows, it increases substantially at hightraffic flows.

JEL Classification: C14, C80, D62, R40

Keywords: Road Traffic Accidents, Traffic Flows, Accident Externalities

Acknowledgements: We would like to thank, without implication, the Department ofTransport for giving us access to the automatic count data used in this study. Particular thanksare due to Daniel Aromire for his assistance in the provision and explanation of these data.The accident data were supplied by the ESRC Data Archive at the University of Essex.Neither the original collectors of the accident data nor the Archive bear any responsibility forthe analyses or interpretations presented here. This research was funded in part by theTRENEN project of the European Commission’s Fourth Framework RTD Programme, DGVII (Project ST-96-SC-116). Finally, we are grateful to Alan Carruth for his useful commentson an earlier draft.

Correspondence address: Dr. John Peirson, Department of Economics, Keynes College,University of Kent at Canterbury, Canterbury, KENT CT2 7NP, UK. email: jdp1@ukc.ac.uk;tel: +44 (0)1227 823328; fax: +44 (0)1227 827850.

2104数学建模美赛A 交通流 安全性 参考资料 交通量

ROAD ACCIDENTS AND TRAFFIC FLOWS:AN ECONOMETRIC INVESTIGATION

1.

Introduction

The costs of road accidents are generally regarded as being considerable and they are thereforean important element in the analysis of transport projects and the formation of transport policy(Evans, 1994; Department of Transport, 1996). For the United Kingdom, the annual total costshave been estimated at between £5 billion and £26 billion (see Maddison et al. 1996; Pearce,1993; Fowkes et al., 1990; Hopkins and O’Reilly, 1993; Hansson and Marckham, 1992 andNewbery, 1988). New transport projects and polices affect the number of road accidents at themargin. Thus, it is important to investigate the marginal external accident costs of additionalroad traffic rather than total or average accident costs.

There are three principal stages in the estimation of the external costs of road accidents(Maddison et al., 1996 and Peirson et al., 1998). The first stage is to identify the functionalrelationship between accidents and vehicular flows. Vickrey (1968, 1969), Jones-Lee (1990),Newbery (1987, 1988), Vitaliano and Held (1991) and, more recently, Jansson (1994) andSchefer and Rietveld (1997) can be regarded as the significant contributors to the formalmodelling of this relationship. Second, the different elements of road accident externalitieshave to be defined. The studies cited above, together with Hansson and Marckham (1992),Jones-Lee et al. (1993) and Persson and Ödegaard (1995), have defined and discussed theseexternalities in a helpful manner. Finally, values have to be placed on these externalities. Theliterature on this subject is extensive (see, for example, Jones-Lee et al., 1985, Jones-Lee,1990 and Jones-Lee et al., 1993). This paper is primarily concerned with the first stage, that ofdetermining the nature of the accident-vehicle flow relationship.

2104数学建模美赛A 交通流 安全性 参考资料 交通量

We construct a unique and novel dataset for this study by amalgamating two disparate sourcesof data. Traffic flow data for the period mid-1993 to end-1995 are taken from the Departmentof Transport’s automated recording devices which are distributed throughout London. Thesevehicle flows are then matched with police data on all road traffic accidents in thecorresponding area during the same period.

The statistical analysis of these data reveals two important findings. Firstly, the accident-flowrelationship varies significantly between different road classifications and broad geographicalareas. This has an important implication for a number of previous studies which have failed toallow for such heterogeneity. Typically, these studies have concluded that there is a near-proportional relation between accidents and flows at all levels of traffic flow and, thus, thereis no apparent accident externality. Such a conclusion may be erroneous since it may resultfrom the aggregation of heterogeneous accident-flow relationships which do not exhibitproportionality.

Secondly, under the simple assumption that occupants of additional vehicles internalise theaverage risk of an accident, the excess of the marginal accident rate over the average ratedetermines the magnitude of the road accident externality. The data indicate that the ratio ofthe marginal accident risk to the average accident risk varies significantly with traffic flow,and, thus, this variation is important. In particular, we show that while the externality istypically close to zero for low to moderate traffic flows, it increases substantially at hightraffic flows. That is, the relationship between accidents and traffic flows is non-linear.

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