Technical studies

This section explains how to conduct various technical studies that are often required during safety analyses (spot speed studies, traffic counts, etc.). Simple procedures are described and their implementation is illustrated by means of practical examples.

Technical Study - Friction

This technical study outlines the main observations that need to be made at a site to verify if road surface friction is adequate and determine the need for instrumented tests. However, it does not describe in their details the numerous testing methods and equipment that have been developed over the years to identify and quantify road surface deficiencies

Some further insights on this topic can be found in the Technical Sheet - Road Surface Condition

Technical Study - Sight Distance

Various sight distance criteria must be met, depending on the type of site under study: stopping, manoeuvring, passing sight distances, etc. These criteria are described in the Technical Sheet - Sight Distance. This engineering study describes how to measure available sight distances.

Technical Study - Spot Speed

In a spot speed study, a sample of speeds are collected at a specific road location in order to determine the speed distribution of vehicles and to calculate some statistics that are used to make engineering decisions. This Technical Study describes various methods of undertaking such studies for varying degrees of automation.

Technical Study - Traffic Conflicts

In most road safety studies, analysts use the information contained on crash reports to identify and understand failures of the road system and then propose appropriate corrective actions.

While these analyses are essential, it is well recognized that crash data suffer from a number of shortcomings and need to be complemented by field observations in order to improve the accuracy of safety diagnoses.

This Technical Study describes how and when to undertake such studies.

Technical Study - Traffic Count

Counts of the number of vehicles passing at a site are often required in road safety analyses, in order to determine if road safety problems may be related to traffic flow deficiencies.

This Technical Study outlines some of the main aspects related to traffic counts that needs to be considered in road safety studies.

Technical Study - Travel Time and Delay

This Technical Study describes how to measure the travel time between two points on a road and the stopped time delays at an intersection. Both measurements are aimed at determining if road users are facing excessive delays. In addition to impeding traffic flow, delays may have an adverse impact on road safety as they increase frustration, leading to hazardous behaviour: choice of unsafe traffic gaps, failure to stop at red lights, hazardous passing manoeuvres, etc.

Delays can be estimated from field observations or, more theoretically, with equations or simulation programs. This engineering study describes two simple field observation methods.