- Shoulder drop-offs are present where the pavement surface and roadside surface differ in height (from a fraction of an inch to several inches). Height differences typically result from rutting erosion, excessive wear, or resurfacing. If a vehicle departs the through lane, a drop-off can hinder a motorist’s efforts to return to the road. When drop-offs exceed the values in Table 16.2, they may require drop-off treatment or qualify for traffic control.
| Table 16.2 Thresholds for Drop-Offs Requiring Treatment | ||||
|---|---|---|---|---|
| Speed (mph) | Drop-Off Height | |||
| 12-ft Lane Width | 11-ft Lane Width | 10-ft Lane Width | 9-ft Lane Width | |
| 30 | 3 in. | 3 in. | 3 in. | 2 in. |
| 35 | 3 in. | 3 in. | 2 in. | 1 in. |
| 40 | 3 in. | 2 in. | 1 in. | 1 in. |
| 45 | 2 in. | 1 in. | 1 in. | 1 in. |
| ≥ 50 | 1 in. | 1 in. | 1 in. | 1 in. |
- Several countermeasures and operational strategies are available to address drop-offs that exceed thresholds listed in Table 16.2:
- In work zones, installation of MUTCD warning signs can alert motorists that drop-offs are present.
- Application of wedge-shaped asphalt material (Safety Edge) between the road and shoulder.
- Where resurfacing contracts are bid separately, contractors should include in the scope of work provision of a 45° angle fillet on the road edge.
- Resurface road surfaces and shoulder surfaces at the same time to prevent drop-offs from forming.
CONTACT:
Chris VanDyke
Research Scientist | Program Manager
chrisvandyke@uky.edu
