A Fresh Look at Roadway Level-Of-Service Issues

The tendency in growth management is to focus on roadway level-of-service standards. However, the methods used to determine roadway levels of service may affect conclusions about road adequacy as much as do the standards to which they are compared. The specific technique used to analyze roadway levels of service can make at least a two-letter grade difference in the outcome. Likewise, the choice of analysis period or peak hour can make a difference of two or more letter-grades. While harder to quantify, the effect of averaging/aggregating levels of service across facilities could be of comparable magnitude. Thus, even adopting the same level-of-service. standards, level-of-service determinations for, say, the City of Miami and Jefferson County, Florida have entirely different implications for motorists. Jefferson County has opted for a by the book approach, comparing the 30th highest hourly traffic volumes on individual roads to the maximum volumes at different levels of service based on Highway Capacity Manual methodology. In contrast, Miami has adopted an innovative but unconventional approach, comparing person-trip volumes for the two highest hours on the average weekday to the practical capacities of multimodal transportation corridors. Among the novel approaches to roadway level-of-service determination reviewed in this article, three seem particularly promising: (1) use of simple regression models to estimate average travel speeds, and from them, arterial levels of service; (2) development of level-of-service measures and standards for travel corridors and traffic districts; and (3) use of lOOth highest hourly traffic volumes as the basis for roadway level-of-service determinations in urban areas