April 8


Guest Post by Bryant Ficek, PE, PTOE, co-author of the Traffic Study Manual.

IMG_0171The typical traffic impact study (TIS) in Minnesota analyzes vehicle operations. The average time at a stop sign, the number of cars stacked in the left turn lane, etc. Today, we are more conscious than ever about multimodal operations and trying to account for pedestrians.

So how does new found appreciation for other modes of traffic fit into the typical TIS?

Currently, the Highway Capacity Manual has a method to determine Level of Service (LOS) for pedestrians. Florida and a couple other states also have their own methodology to follow for other modes of travel. However, in Minnesota, considering pedestrian operations is not a part of our guidelines.

Unless government agencies start calling for it, accounting for pedestrian LOS in your TIS proposal may price you out of the job.

This issue becomes even more confusing when intersection counts and observations show no current pedestrians. Why plan for pedestrians when no one is walking? This is particularly true in suburban areas where driving, even a few blocks, is still prevalent. But I’m a big believer in the “if you build it, they will come” philosophy. Pedestrians may not be crossing the street because the sidewalk or trail is not available or connected to anything yet. Provide the option and people will use it.

The typical TIS in Minnesota uses Synchro/SimTraffic to analyze the study intersections. For unsignalized and signalized intersections, the volume window has a setting for conflicting pedestrians per hour (and for bicycles, if desired). Signalized intersections also have a setting for the number of pedestrian calls per hour in the phasing window. Other software programs have similar settings for pedestrian activity.

My admittedly limited comparison of results with and without pedestrians shows the increase of at least a half second in delay and one or two vehicles in the queue. The impact of pedestrians on the vehicle delays and stacking will gradually increase as the volumes increase at an intersection (as you would expect).

Given the expected impact on results, I include pedestrian crossings as part of my TIS intersection analyses and I believe you should too. If I don’t have any information on pedestrians, I will include 5 conflicting pedestrians, and pedestrian calls if at a signal, for every direction.

Besides reflecting my own thoughts on multimodal activity, this allows me to confidently state that pedestrians are considered when asked at Council or public meetings.

(From Mike:  This is an admittedly minimalist approach Bryant and I use.  I expect we’ll do more as the multi-modal aspects of the Highway Capacity Manual become more universally adopted – i.e. built into our analysis software packages.)

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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