In a temporary traffic control zone, what is the length of a taper to close a single lane on a 70 mph freeway with 12-foot lane widths?

The correct length of a taper for closing a single lane on a 70 mph freeway with 12-foot lane widths is 840 feet. Tapers are critical in traffic control because they facilitate the safe merging of vehicles into an adjacent lane or the safe lane closure, allowing drivers adequate distance to adjust their path.

In determining the taper length, the general rule of thumb is to use the formula that accounts for both the speed of the roadway and the width of the lane being closed. For freeway conditions, the taper length is typically calculated as the speed in mph multiplied by a factor that accommodates safety and driver reaction time.

In this case, using the metric for a 70 mph speed limit and considering the standard lane width of 12 feet, the appropriate formula results in a taper length of 840 feet. This calculation is aligned with guidelines from agencies such as the Manual on Uniform Traffic Control Devices (MUTCD), which provide information based on empirical data to ensure safe transitions for vehicles.

Proper taper lengths are crucial to prevent abrupt lane shifting, which could lead to accidents or compliance issues in high-speed environments. This understanding highlights why 840 feet is the correct choice for this scenario.