Module 6: Highway Safety and Accident Analysis

Question 1

The average 24 hr traffic counts collected every day in the year.

Answer 1

Average Annual Daily Traffic (AADT)

Question 2

They are used to estimate highway user revenue, compute accident rates, and establish traffic volume trends.

Answer 2

Average Annual Daily Traffic (AADT)

Question 3

The average 24 hr traffic counts collected over a number of days greater than one but less than a year.

Answer 3

Average Daily Traffic (ADT)

Question 4

It measures the amount of travel for all vehicles in a geographic region over a given period of time.

Answer 4

Vehicles Miles of Travel (VMT)

Question 5

Formula for Accident rates for 100 million vehicle miles of travel (HMVM) for a segment of a highway

Answer 5

R = A(100,000,000) / ADT(N)(365)(L)

Question 6

Formula for Accident rates per million entering vehicles (MEV) for an intersection

Answer 6

R = A(1,000,000) / ADT(N)(365)

Question 7

Formula for Severity Ratio

Answer 7

SR = (fatal + injury) / (fatal + injury + property damage)

Question 8

Formula for Critical Crash Rate per Million Vehicle Miles or per Million entering vehicles

Answer 8

CR = (AVR) + (0.5/TB) + (TF) (√(AVR/TB))

Question 9

Formula for Crash Reduction Factor to determine the reduction in crashes

Answer 9

CP = (N)(CRF)(ADT after improvement) / (ADT before improvement)

Question 10

Overall Crash Reduction Factor for multiple mutually exclusive improvements at a single site

Answer 10

CRF0 = CRF1 + (1 - CRF1)(CRF2) + (1-CRF1)(1-CRF2)(CRF3) …..

Question 11

Formula of TB

Answer 11

(N)(AADT)(365)(L) / 100,000,000