Traffic Studies

By now, you've probably driven over the traffic strips on Hwy 106. This is a State project, not the town. Here is a brief rundown on why these are used:

They're very simple and cheap methods to gather traffic data for road and traffic planning. They're generally put down by local government and/or highways agencies, or companies working under contract to them. Potential questions they could be asking:

• There are planned road works on this road. How much traffic will we need to account for to divert on to other roads?
• There are high rates of accidents near this point. How fast are people generally driving?
• The signals down the road are often getting jammed up. How many cars regularly pass this area?
• Are large numbers of people using this side street as a cut-through to avoid a main road?
• Are the traffic signals further down the road creating enough natural gaps for pedestrians to cross, or do we need a specific pedestrian crossing here?

In short, those tubes are an extremely cheap and effective way of measuring lots of things about traffic for planning purposes. There's also no potentially  identifying information collected, so nobody tends to care about being monitored by them.

*To answer a very common followup question, these lines are usually put down in pairs a few yards apart so that speed can be measured. Measuring speed with a single line is indeed very unreliable because of varying wheelbase lengths, but with two lines you're literally measuring the time to travel between two points which is exactly what speed is. 

Traffic analyst for the NC DOT said: It's part of my job to determine where to lay these tubes throughout the state. In North Carolina, at least, most of those tubes are put down by the state DOTs or contractors working for the state. Every state in the country is required to annually submit a report to the USDOT through HPMS (Highway Performance Monitoring System). The HPMS report can determine the allocation funding to each state from the federal government for highway improvement and maintenance. Traffic counts are about half of this report. The tubes can also be put at specific locations that are being studied for possible improvements. The tubes and system that runs them can actually differentiate 19 different types of vehicles including: motorcycles, cars, light trucks, and all the different varieties of single-unit trucks (dump trucks, box trucks, wreckers, etc), and combo-unit trucks (tankers, logging trucks, and all varieties 18-wheelers). The way you can tell if they are counting solely volume or volume and vehicle type is if there are one or two tubes laid across the road. 

Another traffic analyst commented:  If you see two of these spaced only a few feet apart they are actually taking speed data as well.  In my experience they are primarily used for two reasons. 1. They are expecting to start construction and need data on how many vehicles pass through. 2. They are considering changing the speed limit.