CHARACTERISTICS AND LEVEL-OF-SERVICE ESTIMATION OF TRAFFIC FLOW ON TWO-LANE RURAL ROADS IN FINLAND

An analysis of speed-flow relationships, time headways, and platooning of traffic on two-lane rural roads in Finland was conducted. In addition, the 1985 Highway Capacity Manual (HCM) level-of-service (LOS) calculation procedure was evaluated under Finnish road and traffic conditions. The speed-flow relationship on Finnish roads was found to be linear and not as steep as that given in the HCM. Simple loglinear regression models were estimated for the percentage of vehicles in platoons and mean platoon length as a function of a 15-min flow rate. A hyperbolic relationship was estimated between the platoon percentage and mean platoon length. The percentage of vehicles in platoons (headway less than 5 sec) was used as an approximation of the percent time delay (PTD) of the 1985 HCM. The analysis of the HCM LOS calculation procedure suggests that the service flow rates corresponding to the PTD values given in the HCM are clearly higher in Finland than in the United States. One reason for this finding may be that the speed-flow relationship and the adjustment factors of the HCM are both calibrated for U.S. road and traffic conditions.