HSM Equations: Rural Multilane Highways

UNDIVIDED ROADWAY SEGMENTS:

  1. Equation 11-2: Crash Prediction Model for UNDIVIDED roadway segments
  1. Equation 11-7: SPF to predict crash frequency for base conditions on UNDIVIDEDroadway segments using coefficients from Table 11-3
  1. Equation 11-13: CMF for Lane Width on undivided roadway segment (Use Table 11-11)
  1. Equation 11-14: CMF for Shoulder Width & Type on undivided roadway segment (Use Tables 11-12 and 11-13)
  1. CMF for Sideslopes on undivided roadway segment
  1. Equation 11–15: CMF for Lighting undivided roadway segment (recommend replacing noted default values with local data if available)
  1. CMF5ru—Automated Speed Enforcement ,
  2. CMF5ru = 0.83 for fatal and injury crashes
  3. CMF5ru = 0.95 for total crashes

DIVIDED ROADWAY SEGMENTS:

  1. Equation 11-3: Crash Prediction Model for DIVIDED roadway segments
  1. Equation 11-9: SPF to predict crash frequency for base conditions on DIVIDED roadway segments using coefficients from Table 11-4
  1. Equation 11-16: CMF for Lane Widthfor divided roadway segments
  1. CMFs for Right Shoulder Width: The SPF base condition for the right shoulder width variable is 8 ft. If the shoulder widths for the two directions of travel differ, the CMF is based on the average of the shoulder widths. The safety effects of shoulderwidths wider than 8 ft are unknown, but it is recommended that a CMF of 1.00 be used in this case
  1. A CMF for median widths on divided roadway segments of rural multilane highways is presented in Table 11-18 based on the work of Harkey et al. (3). The median width of a divided highway is measured between the inside edges of the through travel lanes in the opposing direction of travel; thus, inside shoulder and turning lanes are included in the median width. The base condition for this CMF is a median width of 30 ft.

  1. Equation 11-17: CMF for Roadway Lighting (recommend replacing noted default values with local data if available)
  1. CMF5rd—Automated Speed Enforcement ,
  2. CMF5rd = 0.83 for fatal and injury crashes
  3. CMF5rd = 0.94 for total crashes

RURAL MULTILANE INTERSECTIONS:

  1. Equation 11-4: Crash Prediction Model forall intersection types in Chapter 11:
  1. Equation 11-11: The SPF for base conditions at all intersections using the appropriate a, b, and c coefficients in Tables 11-7 and 11-8

  1. CMFs for total crashes for intersection skew angle;
  2. Equation 11-18 : At three-leg intersections with stop-control on the minor approach
  1. Equation 11-20: At four-leg intersection with stop-control on the minor approaches
  1. CMFs for presence of Left-Turn Lanes:

  1. CMFs for presence of Right-Turn Lanes

  1. Equation 11-22: CMF for Intersection Lighting (recommend replacing default values with local values if available)
  1. Equation 11-5 for total estimated number of crashes within the network or facility limits during a study period of n years: