About one mile into the twisties, while climbing Yarnell Hill, the road makes a left turn. On the right is an armco barrier. Behind that barrier are makers which can cannot be seen by a motorist, but can be observed by law enforcement from the roadway in the distance where it zig zags up the hill. LEOs normally park on the higer level and time vehicles as they go by these markers, making a viual observation of speeds.

The speed limit used to be 55 mph in this area, however, in recent years it has been reduced to 35 mph. The roadway consists of two lanes travelling in the same direction, so the speed is abnormally slow. Over the years many bike riders have charged up Yarnell at high speeds resulting in numerous accidents, which has lead the Police to clamp down.