What Are Those Squiggles of Tar You See on Roads?

Driving through towns can provoke a series of questions. Why is this person going so slowly? Does anyone own that dog? What are those brightly colored balls doing on those power lines? And why do roads appear to be covered in squiggles of tar?

The arterial lines are a common sight on paved roadways, spreading indiscriminately through the lanes. They’re part of the seemingly endless cycle of keeping roads in operable shape.

The tar (actually a polymer mix) is applied to asphalt that has developed cracks due to normal wear and tear from traffic. Sometimes this is due to the volume of vehicles passing over roads. Other times, seasonal weather changes can cause the pavement to contract. Different kinds of cracking can occur, from fatigue cracking—which typically requires a comprehensive resurfacing—to reflection cracking that happens as a result of the concrete and asphalt layers shifting. Edge cracking is the wear you see along the margins of the road.

The filler is typically the most effective and quickest method of resolving the cracks before they become a road hazard—costing about $2500 per mile, compared to $60,000 per mile for a brand-new surface.

While halting a massive crack in its tracks is fine for cars, motorcycles are another story. Because the squiggles create a slightly raised bump, two-wheeled vehicles need to be careful about running over them. Bikers have a derisive term for the patch jobs: tar snake.

In addition to changing the surface, the mix can become slick in bad weather, leading motorcyclists to lose control of their bikes. They can also allow for foreign objects to “sink” into their pliable material, creating further hazards. It’s advisable for bike enthusiasts to slow down when they see the lines coming up in their path.

The tar squiggles are different from the black rubber tubes you often see on roadways, which are used by officials to measure traffic.

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