Safety Evaluation of Edge-Line Rumble Stripes on Rural Two-Lane Horizontal Curves

Chapter 2. Objective

The research described in this report examined the safety impacts of ELRSs on rural horizontal curves in Kentucky and Ohio with the objective to estimate the safety effectiveness of this strategy as measured by crash frequency. Excluding intersection-related and animal crashes, the study included the following crash types:

• Total (all types and severities combined).
• Injury (K, A, B, and C injuries on the KABCO scale).
• ROR (all severities combined).
• Nighttime (including dusk and dawn; all severities combined).
• Nighttime ROR (including dusk and dawn; all severities combined).

A further objective was to address questions of interest including the following:

• Do effects vary by level of traffic volumes?
• Do effects vary by posted speed limit?
• Do effects vary by paved shoulder width?

Other questions included the following:

• Are crash migration effects evident?
• Are spillover effects evident?

The evaluation of overall effectiveness included the consideration of the installation costs and crash savings in terms of the B/C ratio.

Meeting these objectives placed some special requirements on the data collection and analysis tasks, including the need to do the following:

• Select a large enough sample size to detect, with statistical significance, what may be small changes in safety for some crash types.
• Identify appropriate untreated reference sites.
• Properly account for changes in safety due to changes in traffic volume and other nontreatment factors.
• Pool data from multiple jurisdictions to improve reliability of the results and facilitate broader applicability of the products of the research.