Trick for Estimating Cut Through Traffic

Green street sign reading, "Short cut this way"

Cut through traffic is a common complaint to a city engineering department.  This situation occurs when residents think commuters are using the city street they live on to get around congested roads.  The complaint pops up a lot when there’s nearby road construction that’s altering traffic patterns.

We’ve done several complicated origin-destination studies to determine the rate at which motorists are cutting through a neighborhood.  This involves writing down the license plates of vehicles at entry/exit points to the neighborhood during the morning and evening peak periods.  Then searching the license plate designations to match up motorists entering at one point and then shortly leaving the neighborhood at an exit point.

This license plate matching can also be done by recoding the plates with HD cameras and using license plate matching software, but I don’t know of an economical portable system that does this.  I believe The Traffic Group and a couple of other data collection firms may have homemade video systems to do this.

There are also several Bluetooth/Wi-Fi tracking systems that claim to be able to do O-D studies, but I’m very skeptical of them because of their low sampling rates.  It seems like the cut through percentages could be off by several orders of magnitude due to sampling errors.

I recently saw a study that SEH did last year that used a clever work around.  They collected hourly tube count data along several roads within a neighborhood.  It was suggested one road within the neighborhood was used as a cut through route.

The non-cut through routes all had p.m. peak hour volumes that totaled about 10% of the daily traffic volumes, which matches the standard industry norm/rule of thumb.  The alleged cut-through route had a peak hour volume that was about 25% of the daily traffic volume.  SEH surmised that the extra 15% between the normal 10% rate and the 25% rate was cut through traffic that was using the street as a short cut.

I had not seen this technique used before nor had I thought of it.  Although it’s not a precise measurement of the cut-through traffic, I believe it’s a clever low cost way to determine if a residential street has a cut through traffic issue.