Current guidelines arguably do not properly address how much high-occupancy vehicle (HOV) lanes should be prioritized over general-purpose (GP) lanes. This study develops two schemes for HOV and GP lanes by utilizing the concept of “speed equilibrium,” which determines whether HOV lanes are under-prioritized, over-prioritized, or well-prioritized. The first scheme incorporates average vehicle occupancy with speed priorities, reflecting the HOV core value of carrying more persons in fewer vehicles; HOV lanes maintain higher equilibrium speeds than GP lanes, but the differences decrease as traffic speeds decrease from free flow to jam states. The second scheme is a revision of the existing HOV principle: equilibrium built upon the principle of time saved leads to increasingly greater HOV speeds relative to GP lane speeds, as traffic volumes increase. Both schemes are visualized in three-dimensional data plots to illustrate the effects of individual traffic variables. Using only a single measure, i.e., speed, ensures inferior HOV priority with respect to mobility and reliability. Observed freeway data were applied to the two schemes, and the results can be used to determine the necessity of HOV policy adjustment. The schemes are complimentary to current HOV operational assessments.
The Transportation Research Board (TRB) 93rd Annual Meeting, 21p.