Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
Table 4.6-1
Existing and Estimated Future Traffic Volumes
Location
Year of
count
Traffic count
(vehicles/day)
Year 2008 Estimated Traffic
(beginning of Demolition)
(vehicles/day) a
SR 141 (north of SR 141 spur) 2004 4,000 4,162
SR 141 (south of Glenwood Highway) 2004 2,400 2,497
SR 14 (west of SR 141 intersection) 2005 6,500 6,697
Powerhouse Road (0.3 miles west of SR 141) 2003 108 114
Graves Road - 50 (estimated) 55 (estimated)
Northwestern Lake Road (east of Bridge) 2003 939 987
Cabin Road -- -- --
Notes: State road counts (SR 14 and SR 141) were included in the Annual Traffic Report (WSDOT 2005). Other roadway
counts were provided by Klickitat County.
a Estimates of 2008 traffic are based on known traffic counts and applying a 1percent growth rate from the last known
years’ traffic count and projected to 2008.
Existing Level of Service
Roadway Level of Service
Using the highway segment analysis for a 55 mph two-lane rural highway (SR 141 and
SR 14), the LOS of the roadway segment can be calculated. LOS is an estimate of the
performance efficiency and quality of a roadway as established by the Transportation
Research Board’s Highway Capacity Manual (2000). The system used in the manual
measures the degree of delay along segments of roadway and at intersections using the letter
rating “A” for the least amount of congestion and letter rating “F” for the largest amount of
congestion, as shown in Table 4.6-2 for segments and Table 4.6-3 for intersections. An LOS
of C or better is typically considered to be acceptable for a rural setting such as found in this
project. If the LOS falls below the allowable threshold, improvements are required to
improve the capacity of the intersection or roadway section in question.
Table 4.6-2
Level of Service Standards for Roadways (per lane per hour)
Facility Type Free-flow Speed A B C D E
Freeway 55 mph 550 880 1,320 1,744 2,250
Principal Arterial 50 mph 540 900 1,260 1,503 1,800
45 mph 510 850 1,190 1,419 1,700
35 mph 453 756 1,058 1,261 1,600
30 mph 378 630 882 1,051 1,500
Minor Arterial 35 mph 398 664 928 1,105 1,400
30 mph 369 616 862 1,025 1,300
20 mph 284 474 663 789 1,000
Collectors 30 mph 398 663 927 1,105 1,400
25 mph 341 568 795 947 1,200
Local Streets 25 mph - - 250 - -
Source: Transportation Research Board (2000), Table 12-15
4.6-5