The Highway Capacity Manual (HCM) is the authoritative source providing state-of-the-art methodologies for evaluating highway, transit, bicycle, and pedestrian facilities. Default values are used to represent input parameters when the input parameters are difficult to measure or estimate. A default value is a representative value that may be appropriate for estimating an input parameter in the absence of local data. Before this study was done, no nationwide research effort had been conducted to assemble field measurements to determine whether the default values in the HCM represent typical field conditions. A sensitivity analysis was conducted for the input parameters in HCM 2000 that influence the service measures calculated in the HCM methodologies. Nineteen of these input parameters were determined to have a high degree of sensitivity in influencing the service measure results. These sensitive input parameters influence the service measures for the following HCM chapters: Urban Streets, Signalized Intersections, Pedestrians, Bicycle Paths, Multilane Highways, and Basic Freeway Segments. Based on the assembly of a nationwide database, specific default values were recommended for heavy vehicle percentages and peak-hour factors for uninterrupted flow facilities (freeways, multilane highways, and rural two-lane highways). It is recommended that default values for some input parameters continue to be developed based on existing HCM guidance. Other input parameters should be based on field measurements obtained from design plans. Additional guidance is provided to aid in the selection of default values based on the review of recent research documents.
[1]
Ahmed Al-Kaisy,et al.
Examination of Effect of Driver Population at Freeway Reconstruction Zones
,
2001
.
[2]
T. Sando,et al.
Site Characteristics Affecting Operation of Triple Left-Turn Lanes
,
2003
.
[3]
Traffic Congestion.
Traffic Congestion and Traffic Safety in the 21st Century: Challenges, Innovations, and Opportunities
,
1997
.
[4]
Martin T. Pietrucha,et al.
Field Studies of Pedestrian Walking Speed and Start-Up Time
,
1996
.
[5]
Wei Huang,et al.
DEVELOPMENT OF DRIVER POPULATION FACTORS FOR FREEWAY CAPACITY ESTIMATION
,
1997
.
[6]
Leonard,et al.
OPERATIONAL CHARACTERISTICS OF TRIPLE LEFT TURNS
,
1994
.
[7]
Andrew Thomas,et al.
Double Left-Turn Lanes in Medium-Size Cities
,
1999
.
[8]
K. Kagolanu,et al.
Saturation flow rates of dual left-turn lanes
,
1994
.
[9]
Loren Staplin,et al.
Guidelines and Recommendations to Accommodate Older Drivers and Pedestrians
,
2001
.
[10]
Andrea R. Bill,et al.
Recommended Walking Speeds for Pedestrian Clearance Timing Based on Pedestrian Characteristics
,
2006
.
[11]
K. Fitzpatrick,et al.
Another Look at Pedestrian Walking Speed
,
2006
.
[12]
John D Zegeer.
FIELD VALIDATION OF INTERSECTION CAPACITY FACTORS
,
1986
.
[13]
R W Stokes,et al.
SATURATION FLOWS OF EXCLUSIVE DOUBLE LEFT-TURN LANES
,
1986
.