Seven experiment designs addressing problems of safety and capacity on two-lane rural highways. Volume IV: Experimental design to develop and evaluate remedial aids to urban drivers of slow moving vehicles on a grade.

Past studies have shown that as the speed differential between two vehicles traveling in the same direction increases, the accident rate soars. This speed differential is commonly found with a large vehicle ascending a grade being overtaken by a faster vehicle. In this volume, an experimental design was developed to evaluate a series of active and passive warning devices, including roadside and vehicle-mounted devices. A state-of-the-art survey and bibliography are included. A questionnaire, designed to appraise motorists' reactions to these devices, is appended.