This is the report of a review of published data on the relationship between accident frequency and access frequency, or density, and hence the accident effects of different levels of access management (i.e. the control over frequency and location of driveways, minor junctions, median breaks and so on). The primary purpose of access management is to regulate the incidence of turning conflicts, speed differentials within the arterial flow, and side friction. Protecting road safety is the key motive for access management, but it can also be shown to have significant highway efficiency benefits. Despite the apparent quantity of material available on this subject, there is a surprisingly limited range of data to help practitioners anticipate the safety effects of access management in specific cases. The report examines the most useful available examples of recorded data on the effects of access management to indicate some general relationships. The range and general trend of the data are evident, even in this comparatively small body of literature. While the information available helps to contribute to the rationale for access management, and to suggest the broad trend in likely accident experience for different levels of access, it is as yet of limited use in detailed evaluation of specific cases because the actual accident experience at any specific location will be affected by other factors. Research and data collection to improve our understanding of access-accident relationships is strongly recommended. (A)
Abstract