Colored entrance treatments for rural traffic calming : tech brief.

Hallmark, Shauna L.; Knickerbocker, Skylar; Hawkins, Neal · 2013 · ROSA P / Iowa State University. Institute for Transportation

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Summary

This technical brief addresses the challenge of traffic calming in small rural communities, which often lack the engineering resources to effectively manage speeding at community entrances. Drivers transitioning from high-speed rural roadways to low-speed town centers frequently fail to adjust their speeds due to a lack of visual cues, leading to safety risks for pedestrians and local traffic. The study evaluates the effectiveness of colored entrance treatments as a low-cost intervention to signal this change in roadway character and encourage speed reduction. The research was conducted in three rural Iowa communities: Jesup (east and west entrances) and Ossian (north entrance). The treatment design consisted of two phases. The initial phase involved installing red colored boxes approximately 12 feet tall with 8-foot lettering, spaced 28 feet apart, to reinforce the posted speed limit. These boxes were constructed from thermoplastic, high-friction material with glass beads for visibility. Twelve months later, white "dragon’s teeth" markings were added upstream of the colored boxes to lengthen the treatment area and provide visual narrowing. Speed and volume data were collected using pneumatic road tubes (JAMAR FLEX HS counters) for 24 to 48 hours under dry conditions, comparing pre-installation speeds to post-installation speeds at each site. The results indicated that the initial colored entrance treatment alone was effective in reducing speeds. Mean speeds decreased by 1.0 to 2.3 mph, and 85th percentile speeds dropped by up to 2 mph across all sites. Significant reductions were observed in the proportion of vehicles exceeding the speed limit: the fraction of vehicles traveling 5 or more mph over the limit decreased by up to 49%, those traveling 10 or more mph over decreased by up to 60%, and those traveling 15 or more mph over decreased by up to 100%. However, the subsequent addition of the dragon’s teeth markings did not yield statistically significant further improvements in speed reduction compared to the initial phase. The speed reductions remained similar, suggesting that the colored boxes were the primary driver of the behavioral change. The study concludes that colored entrance treatments are a viable traffic-calming strategy for rural communities, providing clear visual cues that prompt drivers to slow down upon entering town limits. The findings suggest that while the colored boxes are effective, the additional cost and complexity of installing dragon’s teeth markings may not be justified given their lack of incremental benefit. This approach offers a practical solution for communities with limited resources, avoiding the pitfalls of inappropriate measures like stop signs or overly aggressive speed transition zones.

Key finding

The addition of white dragon's teeth markings to existing red colored entrance treatments did not significantly improve speed reduction effectiveness compared to the red treatments alone.

Methodology

on_road

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• perceptual countermeasures
• speed management
• signage environment