FLOOD07468

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: The Design of Encroachments on Floodplains Using Risk Analysis
• Date: 10/1/1980
• Prepared For: USDOT
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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There are three subcategories of traffic-related losses which might occur:

(1 ) Increased running cost due to the detour.
(2) Lost time of vehicle occupants.
(3) Increased accidents on the detour.

Much of the data necessary to assess these losses is available in the highway
agencies planning and/or traffic engineering units.

7.3.2 Increased Running Cost

This cost represents the difference between the running cost on the detour
and the normal route. It is a function of ADTE, travel distance, duration of
detour, design speed and vehicle distribution. The vehicle distribution,
number of cars, trucks, semitrailers etc., used in the analysis may be a
standard distribution or one based on an actual traffic distribution in the
study area. Running costs are computed for the passenger cars in the distri-
bution and these costs adjusted to reflect the costs for the other classes of
vehicles in the traffic distribution.

To obtain the losses due to increased running costs, it is necessary
to compute the running costs over the normal route and the detour. The
difference in these values is the additional cost or economic loss to the
users of the facility.

Running cost (RC) is computed by:

RC = (Time)(ADTE~~LenBth)(Unit Cost)
,00

Losses from running costs (RCL) are then:
RCL = (RC for Detour) - (RC for Normal Route)

Where:

Time (Duration of detour) is in hours
ADTE is in vehicles per day
Length is in miles
Unit costs are in dollars per 1000 vehicle miles

Example: For the Row Creek example, the travel distances are 5 miles for the
normal route and 10.3 miles for the detour route. Travel speeds are 55 mph
for the normal route and 35 mph for the detour. The types of vehicles in the
traffic distribution are:

(1) Passenger cars (70% of ADTE)
(2) Commercial delivery trucks (20% of ADTE)
(3) Semitrailer trucks (10% of ADTE)

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