Week 3: Review of the Signal Justification Report

This week, I got the full 77-page signal justification report that Wells + Associates wrote for the BASIS intersection. It’s the same study I mentioned last week, but now I’ve actually read through it instead of just skimming. The report breaks down all nine MUTCD signal warrants, which are basically requirements that determine whether an intersection legally needs a signal. Only two warrants were met: four-hour vehicular volume and peak hour delay. Although the other seven warrants weren’t met, the traffic volumes and delays were bad enough to justify the signal anyway.

What stood out to me was how detailed the data collection was. They counted every vehicle for 13 hours straight and even did a right-turn-on-red adjustment where they reduced certain volumes by 25% based on driver behavior at a nearby signal. The intersection currently operates at Level of Service F during the evening rush, which is the worst rating possible. With a signal, they’re projecting it improves to LOS B. They also analyzed a roundabout alternative that would perform even better at LOS A, though cost or space constraints likely ruled it out.

I also have the actual Synchro files that Wells + Associates used for this study, which means I can open their model and see exactly how they set everything up. My plan for this week is to explore the existing model, figure out how the software works, and start testing some basic changes to see what happens to the results.