ABSTRACT
This chapter reviews the impact of road user behavioural adaptation on cost-benefit analyses. Cost-benefit analyses are policy impact assessments in which all relevant impacts of a road safety measure are converted to monetary terms to enable a comparison of benefits and costs. Cost-benefit analyses are based on normative economic welfare theory. Implementing a certain measure is recommended if its benefits are greater than its costs, discouraged if benefits are smaller than costs. Multiple policy impacts are usually included in cost-benefit analyses; relevant impacts are all those that influence welfare, irrespective of whether the impact is intentional or not. Thus, reducing unintended effects of travel, such as crashes and traffic noise, will improve welfare and should therefore be included in a cost-benefit analysis. Impacts that are typically included in cost-benefit analyses are: changes in the number and severity of crashes, changes in travel speed, changes in traffic volume, shifts between modes of travel, changes in air pollution, and changes in traffic noise. These impacts appear on the benefit side of analysis (as savings if an unwanted impact, such as crashes, are reduced, but as negative benefits if an unwanted impact increases). The term ‘cost’ in cost-benefit analysis refers to the costs of implementing a measure. Behavioural adaptation among road users will, depending on the form it takes, influence costbenefit analyses principally by influencing the impacts that will be included in such
20.1 Introduction .................................................................................................. 371 20.2 Rules of the Game for Cost-Benefit Analysis .............................................. 372 20.3 Case 1: Bright Road Surfaces ....................................................................... 374 20.4 Case 2: Road Lighting .................................................................................. 375 20.5 Case 3: Airbags and Antilock Brakes ........................................................... 377 20.6 Case 4: Demand for Safety Measures Based on a False Sense of Safety .......378 20.7 A Conceptual Framework for the Treatment of Behavioural Adaptation
in Cost-Benefit Analyses ..............................................................................380 20.8 Conclusions and Recommendations ............................................................. 383 References ..............................................................................................................384
