Delta Region Transportation Development Program: Rural Safety Innovation Program Evaluation – Final Report

Chapter 5. Conclusions

Many of the safety improvement projects implemented as part of the RSIP-DRTDP were able to achieve the overall goal of USDOT's Rural Safety Initiative to improve safety on rural highways by decreasing loss of lives and injuries.

In Mississippi (RSIP Project 27), the installation of centerline rumble strips on rural two- lane roads, where shoulder rumble strips were already present, resulted in a decrease in SVROR (right or left), sideswipe-opposite direction, and head-on crashes. The dual application of centerline and shoulder rumble strips on rural two-lane roads resulted in a 35-percent reduction (SE=10.5) in total target crashes and a 40-percent reduction (SE=12.3) in FI target crashes. The results highlight the need for additional research on quantifying the safety effectiveness of individual treatments installed in combination. The results from this research suggest that the current state of practice approach for estimating the safety effectiveness of countermeasure combinations (i.e., multiplying together CMFs of individual countermeasures to estimate the combined CMF) may overestimate the effectiveness of countermeasure combinations.

In Louisiana (RSIP Project 37), improved signing and pavement markings at rural stop- controlled intersections effectively reduced total and FI intersection and intersection-related crashes. The improved signing and pavement marking treatments resulted in the following crash reductions at the respective intersection types:

• Three-leg stop-controlled intersections on rural two-lane roads
  • 67-percent reduction in total crashes (SE = 4.3)
  • 56-percent reduction in FI crashes (SE = 8.9)
  • 30-percent reduction in total target crashes (SE = 10.3)
• Four-leg stop-controlled intersections on rural two-lane roads
  • 53-percent reduction in total crashes (SE = 10.3)
  • 64-percent reduction in FI crashes (SE = 12.2)
  • 33-percent reduction in total target crashes (SE = 17.3)

Target crashes included rear-end, right-angle, and turning crashes. When comparing the combination of improvements implemented at the treatment sites, the primary treatment that likely had the greatest effect on reducing crashes was the installation of oversized advance warning signs or oversized stop signs. Secondary treatments including new route marker signs and stop bars likely contributed less to the safety improvements.

In Arkansas (RSIP Project 33), the safety evaluation of cable median barrier installed on rural interstates was able to demonstrate beneficial effects on all crash types and severities. In particular, following installation of cable median barrier on rural interstates, the results showed a 49-percent reduction in FS crashes that was marginally significant at the 88-percent confidence level.

For the RSIP projects for which the safety evaluation yielded unreliable estimates (RSIP Project 36) or the safety effectiveness could not be completed due to insufficient data (RSIP Projects 28, 31, and 34), there is insufficient evidence at this time to reliably determine treatment effectiveness.

Finally, highlights of the lessons learned by TDOT (RSIP Project 25) and MoDOT (RSIP Project 32) in developing a sign inventory system and installing dynamic message signs and closed- circuit video, respectively, will benefit other agencies interested in similar programs. In particular, knowing of the logistical difficulties encountered by TDOT during data collection and post-processing of the sign inventory data will help other agencies during the planning stage of implementing a similar project within their jurisdictions. Also, the need to coordinate with electric companies early in the planning and project development phases is important information for other agencies planning to implement projects that involve installation of DMSs and CCTVs. From a qualitative perspective, the RSIP projects implemented by TDOT and MoDOT were a success and benefitted the respective agency. The knowledge gained from the evaluation of the RSIP-DRTDP projects can benefit other highway agencies when making funding decisions concerning future safety improvement projects and programs.