By Mike Spack, PE, PTOE
I’m occasionally hired to review traffic studies other consultants have prepared. Here’s a list of questions I use when I have to go through a traffic study:
- Project Description Review. Does the traffic study have a complete project description?
- Type of proposed uses
- Size – building square footages, units, etc.
- Build in phases? When is full occupancy expected?
- Proposed site plan
- Â Study Years. Do the study horizon years make sense?
- Â Study Hours. Â Are the study hours reasonable?
- Â Other Intersections. Are all possibly impacted intersections studied?
- Â Trip Generation Data. Is the trip generation data reasonable? Is new or specialized trip generation data needed for the study?
- Â Trip Distribution Pattern. Does the trip distribution pattern seem reasonable (this is the most subjective part of any traffic study – pay special attention)?
- Â Analysis Methods. Do the analysis methods seem reasonable (micro-simulation if closely spaced intersections or queuing issues)?
- Â Forecasting Method. Is the method for forecasting future years reasonable (typically based on a growth rate assumption)?
- Â Other Developments. Are there other nearby developments that should be accounted for in traffic forecasts?
- Â Forecast Data. Do the forecasts make sense (peak hour volumes going between intersections balance, are the trips from the site distributed per distribution pattern, daily forecasts are +/- 10 times peak hour volumes, etc.)?
-  Data Accuracy. Is the technical data in the appendices accurate? Make sure the peak hour factor used in Level of Service analysis is reasonable. Spot check to make sure the turning movement volumes are correct and signal timing plans are reasonable in Level of Service analysis.
- Â Warrant Analysis. If an upgrade in traffic control is recommended, is a warrant analysis included per MUTCD?
-  Access Points. Do proposed access points meet agency access spacing guidelines? If not, full justification is needed for a variance.
-  Right of Way Considerations. Is sufficient right-of-way being dedicated to provide for long term traffic control and roadway geometry that may be needed?
- Â Improvement Funding. If improvements are needed, who’s paying?
- Â Recommendation Review. Do the recommendations make sense (is there a better solution or are superficial improvements being recommended)?
-  Visit the Site. The last thing I do….I go to the site to make sure I didn’t miss anything.
I have created a Traffic Study Manual that is will help you create thorough and thoughtful traffic studies every time. Also, get a free copy of our Trip Generation data with more than 10,000 hours of professionally collected trip generation data at TripGeneration.org.
What considerations do you look at when you review a traffic study? Share your comments below.
I’d add one. Will the development aggravate any existing safety problems? I wouldn’t expect a developer to fix something, but I think it is fair to expect them to do what they can within reason to avoid making it worse.
When I was the traffic engineer in Maple Grove, I saw safety as one of my primary responsibilities. We did a thorough safety audit (I personally drove every street) and we did a crash analysis for the whole city. I kept a list of “hot spots” on my desk to make sure we weren’t aggravating them. I also worked to correct the hot spots.
Several jurisdictions in Minnesota require a safety analysis as part of their traffic studies and I am happy to comply. It is definitely a city’s prerogative to require a safety analysis.
I have a hard time explaining to a developer why they should be paying for a crash analysis if the city/county/state doesn’t require it. This is especially true in a multi-proposal situation where the other firms aren’t proposing a crash analysis.
Hi Mike, Looks like you nailed this one with your checklist. I provide this same service for many of my clients. I was about to call you out on one the most important items…but you mentioned it as the very last point. The site visit is critical (especially during peak hour conditions) and I usually perform this task up front so I have a clear understanding of the peak period traffic conditions before I complete the review.
I also ask the client what the critical issues or hot buttons are with Planning and Zoning or elected officials to make sure those items are adequately addressed in the report.
Hi Mike, Can I add another one? With respect to the topic of “Transportation Planning”, how does the development conform to the city’s Master Transportation Plan? Are they improving their frontages to support the ultimate plan for the corridor(s)?