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the effects of neighbourhood socio-demographic characteristics of both the crash location and

road users' residence, on traffic crashes involving heavy vehicles.

2.7 Summary

This chapter has presented a review of existing crash severity models used to analyse crash
and injury severity in road collisions. In addition, the advantages and disadvantages of the

crash severity models which have been applied in modelling crashes and injury severity
prediction in existing studies have been summarised. According to the literature, the models

which have been used to investigate crash and injury severity include binary outcome
models, ordered discrete outcome, and unordered multinomial discrete outcome models. The

two major types of crash severity outcomes that are normally used for modelling are ordered

discrete outcome and unordered multinomial discrete outcome. The ordered discrete outcome
of the dependent variable is ordinally categorised from low injury to high severity injury or

non-injury to fatal injury. On the other hand, the unordered multinomial discrete outcome
does not take account of ordinal severity injury datasets.

Variables have been used in previous models and the findings of previous studies on crash

and injury severity involving heavy vehicles as well as the existing literature on road
collisions at intersections and mid-blocks have been summarised. In addition, a summary of

existing studies on the influence of neighbourhood socio-demographic characteristics around

crash locations and the neighbourhoods where road users live on traffic crashes has been
provided in this chapter.

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