Highway Performance Monitoring System
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HPMS Field Manual
Appendix N: Procedures for Estimating Highway Capacity
Rural One-Lane Capacity
These highways, though rare, do exist in HPMS. They include facilities with both one-way and two-way operation.
The capacity of these sections should be computed using the procedure for Rural Two-Lane Highways, with the following changes:
The resulting capacity is, by definition, a one-way value.
One-lane highways open to both directions of traffic are extremely rare. For these cases, compute the capacity for one-way operation and divide by 2.
Rural Three-Lane Highway Capacity
These highways have two through lanes in one direction and a single lane in the opposite direction. The through lanes are assumed to cover an extended length and are not auxiliary or truck climbing lanes. (This is consistent with the coding of HPMS data).
It is assumed that these highways operate as a multilane undivided facility in the two-lane direction and as a single direction of a rural two-lane facility in the one-lane direction. The two-way capacity (required by HPMS for these facilities) is then the sum of these two separate capacities.
The capacity for the two-lane direction is computed using the Multilane Highway capacity procedure assuming an undivided cross-section. The capacity for the one-lane direction is computed using the procedure for Rural One-Lane, One-Way Highways.