Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
N (d 1 ) = N (0.10469) = 0.4583
N (d 2 ) = N (-0.10469) = 0.5417
The certainty-equivalent value of reliability is:
rT ( t)
PV ( ,) t Ie − −
= Nd ( ) −VNd
( )
T
2 T 1
= 3.03 mph
The new average speed at which the commuter is willing to travel if unreliability is eliminated
= 36.39-3.03 = 33.35 mph
Time to cover 1 mile at old average speed =
Time to cover 1 mile at new average speed =
Thus, the new certainty-equivalent value in minutes per mile is:
The reduction of the certainty equivalent value from 0.20 minutes per mile (before the ramp
meter installation) to 0.15 minutes per mile (after the ramp meter installation) means that after
the implementation, the commuter is willing to accept less of a reduction in speed in exchange
for eliminating variability. The commuter is willing to give up less to eliminate variability
since the variability has decreased (reliability has improved) after the implementation of the
ramp meters.
Step 4 – Calculate the Value of the Reliability Improvement to the Road User
A. Determine the value of time for different vehicle classes.
B. Calculate the value of the reliability improvement for each vehicle class.
C. Calculate the value of the reliability improvement for the average a.m. peak
period.
D. Calculate the total annual value of the reliability improvement over the length
of the highway for all user groups for the average a.m. peak period only.
A. The value of time for different vehicle classes is shown in Step 1 Part A.
B. The value of the reliability improvement for each vehicle class during the three-hour a.m.
peak period is shown below:
• Passenger vehicles =
6,921 X ($0.30/minute) X (0.20-0.15 minutes/mile) = $103.82/mile
• Trucks = 214 X ($0.83/minute) X (0.20-0.15 minutes/mile) = $8.88/mile
SAMPLE PROBLEM-QUANTIFYING THE ECONOMIC BENEFIT OF IMPROVING TRAVEL-TIME RELIABILITY Page D-10