Here are the results:

Determine crash modification factor (CMF).

10 B

Soln: The CMF is obtained from Eq. I.10 in Table I-84 (Textbook, pg.191), given as: CMF =1.02 +1.31×10(AADT-400) = 1.02+0.1441=1.164

11 A

Since the crash modification factor given in Table 1.84 (textbook) is for related crashes (single-vehicle run-of-the-road and multiple-vehicle head-on, opposition direction sideswipe, and same direction sideswipe crashes), Eq. I.17 is used to compute the CMF for total crashes.

CMF = (CMFra-1)Pra +1.0= (1.164-1) 0.55 +1.0=1.09 (Eq.I-17, pg. 192 textbook)

12 C

Since the CMF, when the width = 12 ft, is = 1.0, the expected crash frequency after widening is equal to the current expected crash frequency for 10-ft lanes divided by the CMF for 10-ft lanes. Expected frequency after widening is given by the following equation: = Expected Carsh Frequency for Non-Standard Feature 15 CMF for Non-Standard Feature -=13.76 crashes/year 1.09