Abstract:
Although the 2000 Highway Capacity Manual (HCM2000) features a completely revised two-lane uninterrupted flow chapter, it does not address two-lane highways in developed areas. The Florida Department of Transportation (FDOT) with the University of Florida (UF) has developed an approach to reasonably deal with these situations and implemented the analysis procedure in an easy to use software program, HIGHPLAN (highway planning). While agreeing with the HCM2000 that the primary service measure for drivers in rural undeveloped areas is the percentage of time spent following other vehicles, use of that service measure does not appear appropriate in small or medium-sized communities. The authors believe that most through drivers probably accept that they need to slow down in developed situations, and they are most concerned with being able to travel at a reasonable speed, not the ability to pass as if they were on an open road. Based on that premise, percent of free flow speed should be the primary service measure in developed areas. Furthermore, the HCM should include a third class of two-lane uninterrupted flow highways (Class III), those in developed situations. This paper includes the basis for the new class of two-lane uninterrupted flow highways, FDOT’s and UF’s recommended level of service thresholds and typical service volumes for these types of facilities, successful applications in Florida, and an overview of the software (HIGHPLAN) implementing the recommendations.
