Rumble strip

Rumble strips are strips of painted, ridged or grooved road surfaces to warn drivers when they stray from their lanes onto the hard shoulder. They are also sometimes used on rural highways to indicate that a stop sign is coming up, especially if there have been several miles or kilometers of stop-free traveling before that point. The strips alert the driver both by causing a tactile vibration and the namesake audible rumbling. Occasionally in the UK, they may be painted horizontally across the road in groups of 5 as a traffic calming method, to slow drivers down.