For a lane closure on a freeway with a 65 mph speed limit, how long should the taper be for a 12 ft wide lane?

The appropriate length of a taper for a lane closure on a freeway is determined by the speed of traffic and the width of the closed lane. In this case, with a speed limit of 65 mph and a 12 ft wide lane, the correct taper length calculation is based on established guidelines.

For a lane closure, the recommended taper length can be calculated using the formula of 10 times the lane width for speed limits up to 45 mph, and for higher speed limits, the length of taper often increases. Generally, for each additional increment of speed, more taper length is needed to give drivers ample time to transition safely.

At a 65 mph speed limit, the taper should be extended significantly to allow vehicles to adjust their speed and maneuver. The recommended taper length for a lane closure at this speed is typically set at 13 times the width of the lane. Thus, using the lane width of 12 ft, the calculation is as follows:

Taper length = Width of lane × 13 = 12 ft × 13 = 156 ft.

However, this calculation varies and is often rounded to standard values determined in traffic engineering manuals. The values in the choices reflect standardized practices, which account for factors such as driver perception and reaction