2H. Highway safety analysis Flashcards
(e.g., crash modification factors, Highway Safety Manual)
How many conflict points are there on a Four-Leg Intersection?
32 Conflict points
8 diverging
8 merging
16 crossing
How many conflict points are there on a T Intersection?
9 Conflict points
3 merging
3 diverging
3 crossing
How many conflict points are there on a roundabout?
8 Conflict points
4 diverging
4 merging
What is CMF and how is it calculated?
CMF = Crash modification factor
CMF = expected avg crash for improved conditions / expected avg crash for existing conditions.
Note: CMF should be less than 1, otherwise the conditions just got worse.
What is the formula in determining crash rates at intersections?
Common exam problem would be to rank intersections by crash rates.
R(int) = [crashes * 10^6] / [ADT * years * 365 (day/yr)]
R(int) = crash rate in million entering vehicles
ADT = Average daily taffic (vpd)
What is the formula in determining crash rates at highways?
Common exam problem would be to rank highways by crash rates.
R(int) = [crashes * 10^8] / [ADT * years * 365 (day/yr) * L(mi)]
R(int) = crash rate in million entering vehicles
ADT = Average daily taffic (vpd)
L(mi) = Length in miles
