Friday, May 8, 2009

Helping colorblind drivers helps everybody

I previously referenced this study from the Kentucky Transportation Center regarding a number of low-cost safety measures for signalized intersections. Here's the complete document:

I took a closer look at it this week and noticed something interesting. A number of colorblind-friendly treatments also provided an overall benefit to the safety at signals.

Double Red Lights

This application creates a "Red T" at the top of the signal head. It's main purpose is to double the visibility of the red indication. For colorblind drivers, it provides additional information that it is the red indication (in addition to its placement at the top of the signal).
  • Total crashes down 2 per year
  • Angle crashes down 1.7 per year
  • Rear-end crashes up 0.5 per year

Advanced Warning Flashers

I had not thought about this one before as a significant colorblind benefit, but I believe it could be. There are times that I don't always know if what I'm seeing three blocks ahead is a traffic signal or just ambient lighting from other sources. Signal Ahead signs (and particularly those discussed in the report with actuated flashers) give me the additional information I need to know what is coming up.

  • Total crashes down 1.4 per year
  • Angle crashes down 0.7 per year
  • Rear-end crashes down 0.6 per year

Reflective Backplates

Backplate installation showed a crash reduction benefit for ALL drivers by adding conspicuity to the traffic signal.

  • Total crashes down 1 per year
  • Angle crashes down 0.4 per year
  • Rear-end crashes down 0.3 per year
Crash Data

Though the reductions seem small, it's important to keep in mind the cost was also very low for these treatments. And though 0.5 crashes per year might sound insignificant, if multiplied times an entire state DOT or large city signal system (sometimes thousands of intersections), significant reductions could be achieved.

The best implementation plan may be modifying policy so any new signal installations (or updgrades) are put in with these measures. High crash locations could also be added to the mix, so that eventually every signal includes these improvements or something similar.

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