Road Safety Audits (RSA)

RSAs: COSTS AND BENEFITS

RSA Costs

Three main factors contribute to the cost of an RSA:

• RSA team costs,
• design team and owner costs,
• costs of design changes or enhancements.

The RSA team costs reflect the size of the team and the time required for the RSA, which in turn are dependent on the complexity of the RSA project. For the RSAs in this case studies project, the following cost components are noted:

• RSA teams were composed of between four and ten persons in this case studies project, but these teams were large since the RSAs served as training exercises for local engineering staff. Without the need for training, the RSA teams would more typically have been composed of three or four persons.
  
  
• Opening and closing meetings, site visits, and RSA analysis sessions were conducted in a three-day period for each RSA.
  
  
• Prior to and following the on-site portion of the RSA, the time required for analysis (such as analysis of collision records, and research on applicable design standards or mitigation measures) and writing the RSA report ranged between 20 and 55 man-hours, with 30 to 40 man-hours being typical. The wide range primarily reflected the number and complexity of the issues identified during the RSA.

For this case studies project, additional RSA team costs were incurred in travel for experienced RSA team leaders. However, typical RSAs would employ local team members, and consequently entail only minor travel costs.

The design team and owner costs reflect the time required for staff to attend the start-up and preliminary findings meetings, and to subsequently read the RSA report and respond to its findings. In addition, staff time is required to compile design drawings and other project or site materials for the RSA team.
The final cost component is that resulting from design changes or enhancements, which reflect the number and complexity of the issues identified during the RSA. Suggested design changes and enhancements, listed in the Appendix (Tables A.1 through A.12) for each of the RSAs conducted for this case studies project, have focused on low-cost improvements or countermeasures where possible.

• Suggested improvements for the four RSAs of existing roads focused mainly on improved signing, signal enhancements, parking and access management.
• Suggested improvements for the four detailed-design RSAs focused on improved signing and pavement markings, minor or moderate geometric changes (such as added auxiliary lanes at intersections), and barrier improvements. It should be noted, however, that one project owner initiated a fundamental reconsideration of its entire project on the basis of the RSA findings, which identified fundamental concerns regarding the net safety benefits of the improvement project.
• Suggestions for the preliminary and planning stage RSAs ranged from minor improvements such as signing, through moderate geometric improvements such as median and gateway treatments, to suggestions related to fundamental issues such as design vehicles, design volumes, and access restrictions.

RSA Benefits

The primary benefits of RSAs are to be found in reduced crash costs as road safety is improved. The costs of automotive crashes are estimated by the US Department of Transportation¹ as:

• $3,000,000 for a traffic fatality,
• $2,290,000 for a critical injury,
• $565,000 for a severe injury,
• $175,000 for a serious injury,
• $45,000 for a moderate injury,
• $6,000 for a minor injury.

Other benefits of RSAs include reduced life-cycle project costs as crashes and the need for retrofitted safety improvements are reduced, and the development of good safety engineering and design practices, including integration of multimodal safety concerns and consideration of human factors in the design.

As mentioned in the recent FHWA/ITE Intersection Safety Issue Brief on RSAs, it is difficult to quantify the benefits of design-stage RSAs, since they aim to prevent crashes from occurring on new or improved facilities that have no crash record. However, when compared with the high cost of motor-vehicle injuries discussed above, the moderate cost of a design-stage RSA suggests that changes implemented from an RSA only need to prevent a few moderate- or high-severity crashes for an RSA to be cost effective.

The benefits of RSAs on existing roads can be more easily quantified, since pre-and post-improvement collision histories are available. As an example, the Road Improvement Demonstration Project conducted by AAA Michigan in Detroit and Grand Rapids (MI), which is based on RSAs of existing high-crash urban intersections and implementation of low-cost safety measures at them, has demonstrated a benefit-cost ratio of 16:1.

Another example of U.S. data on the quantitative safety benefit of RSAs conducted on existing roads comes from the New York DOT, which reports a 20 to 40 percent reduction in crashes at more than 300 high-crash locations that had received surface improvements and had been treated with other low-cost safety improvements suggested by RSAs.

The South Carolina DOT RSA program has had a positive impact on safety. Early results from four separate RSAs, following one year of results, are promising. One site, implementing four of eight suggested improvements, saw total crashes decrease 12.5 percent, resulting in an economic savings of $40,000. A second site had a 15.8 percent increase in crashes after only two of the thirteen suggestions for improvements were incorporated. A third site, implementing all nine suggested improvements, saw a reduction of 60 percent in fatalities, resulting in an economic savings of $3,660,000. Finally, a fourth location, implementing 25 of the 37 suggested safety improvements, had a 23.4 percent reduction in crashes, resulting in an economic savings of $147,000.

The most objective and most often-cited study of the benefits of RSAs, conducted in Surrey County, United Kingdom, compared fatal and injury crash reductions at 19 audited highway projects to those at 19 highway projects for which RSAs were not conducted. It found that, while the average yearly fatal and injury crash frequency at the RSA sites had dropped by 1.25 crashes per year (an average reduction from 2.08 to 0.83 crashes per year), the average yearly fatal and injury crash frequency at the sites that were not audited had dropped by only 0.26 crashes per hear (an average reduction from 2.6 to 2.34 crashes per year). This suggests that RSAs of highway projects make them almost five times more effective in reducing fatal and injury crashes.

Other major studies from the United Kingdom, Denmark, New Zealand, and Jordan quantify the benefits of RSAs in different ways. However, all report that RSAs are relatively inexpensive to conduct and are highly cost effective in identifying safety enhancements.

¹Intersection Safety Issue Brief No. 15 (“Road Safety Audits: An Emerging and Effective Tool for Improved Safety”), issued April 2004 by Federal Highway Administration and Institute of Transportation Engineers.