Vista Ridge Tunnels

The Vista Ridge Tunnels are highway tunnels through the Tualatin Mountains ("West Hills") of Portland, Oregon, USA through a hillside locally known as Vista Ridge which is a half mile (1 km) west of downtown Portland. Sunset Highway, also known as U.S. Route 26, is carried through the tunnels, three lanes in each direction. The average daily combined traffic volume was 145,299 vehicles in 1999 [ cite web
url = http://www.hevanet.com/oti/may99westsidecorridor.htm
title = Analysis of the Westside Corridor Travel Study—Did Westside Light Rail Really Reduce Traffic Volumes?
author = Oregon Transportation Institute
date = November 51999
accessdate = 2007-08-04 ] and 139,300 in 2005. [ cite web
url = http://www.oregon.gov/ODOT/TD/TDATA/tsm/docs/2005_TVT.pdf
title = 2005 Traffic Volumes on State Highways
author = Oregon Department of Transportation
date = 2006-09-20
pages = 60 (84 on page)
accessdate = 2007-08-25 ] They are the busiest tunnels in Oregon [ cite web
url = http://www.oregon.gov/ODOT/HWY/BRIDGE/docs/newstip_2008-2011.pdf
title = 2008-2011 Draft Statewide Transportation Improvement Program—Evaluation of the State Bridge Program
author = Oregon Department of Transportation—Bridge Engineering Section
date = April 2007
pages = 26 (25 on page)
accessdate = 2007-08-25 ] and 12% busier than I-5's 6-lane Interstate Bridge and 2% busier than I-205's 8+ lane Glenn L. Jackson Memorial Bridge. [Glenn L. Jackson Memorial Bridge carries 137,000 average daily traffic; the Interstate Bridge, 124,500. Obtained 2004 values from cite web
url = http://www.oregon.gov/ODOT/COMM/docs/interstate_traffic_counts.pdf
title = Average Daily Traffic on Oregon’s Interstate Highways 1954–2004
publisher = Oregon Department of Transportation
date = May 102006
pages = 2, 4
format = PDF
accessdate = 2007-08-29 ]

The eastbound tunnel is 1001.0 feet (305 m) in length; the westbound tunnel is 949 feet (289 m). Both have 41 ft (12.5 m) of horizontal and 15.58 ft (4.75 m) of vertical clearance. The eastbound tunnel was completed in 1969; the westbound finished a year later. [ cite web
url = http://bridgehunter.com/or/clackamas/910304707353/
title = Vista Ridge Tunnel (#9103+047+07353)
publisher = Historic Bridges of the United States
accessdate = 2007-07-30 ] [ cite web
url = http://www.oregon.gov/ODOT/HWY/REGION2/docs/area5/SaltCreekViaducts/Appendix_A_Highway_Tunnels_of_Oregon.pdf
title = Appendix A: Highway Tunnels of Oregon
author = Updated August 1999 by Rosalind Keeney, ODOT Cultural Resource Specialist; Revised September 2002 by Robert W. Hadlow, Ph.D., ODOT Historian
format = PDF
publisher = Oregon Department of Transportation
date = September 2002
accessdate = 2007-08-04 ]

There is a six percent grade through the tunnels. Most of the tunnels' lengths are straight, though they curve southward at the west ends 35°. [Determined by rotating [http://maps.google.com/?ie=UTF8&ll=45.515527,-122.697174&spn=0.005165,0.010021&t=k&z=17&om=1 satellite image] with photoshop.]

The tunnels were built with ventilation shafts which were never used. Instead, the shafts were later adapted for electrical wiring to improve tunnel illumination but without marring the tunnel's appearance with visible conduit. cite web
url = http://www.sparling.com/news/articles/Tunnel%20Lighting.pdf
title = Tunnel Lighting
author = Jim Degnan, P.E.
work = Roads and Bridges
date = October 2005
publisher = Sparling electrical engineering and technology consulting
accessdate = 2007-08-04 ]

To improve tunnel safety for motorists, and decrease the tunnel lighting requirements, the original tunnel entrance faces were sandblasted to remove white paint and repainted a less luminescent tan color to reduce the range of visual light adaptation required by drivers. At one time there were computer-based electronic light controls, but they were replaced by relatively simple photo detectors and relays for durability and simplicity. The night lighting level is enabled permanently and is supplemented by two or three levels of daytime lighting.

Except directly over the tunnels, the hillsides are steep and undeveloped forest, with some residential development along the top of the ridges. Landslides occasionally occur, but are usually minor and quickly cleared. [ cite web
url = http://www.portlandonline.com/shared/cfm/image.cfm?id=153380
title = News Release: Landslide Repair Work Closes Westbound U.S. 26
publisher = Oregon Department of Transportation
date = April 132007
accessdate = 2007-08-04 ]

The tunnels have been closed to hazardous material transport since November 1, 1994. [ cite web
url = http://www.fmcsa.dot.gov/rules-regulations/administration/rulemakings/12-4-2000.htm
title = Transportation of Hazardous Materials; Designated, Preferred, and Restricted Routes
work = Federal Register: December 42000 (Volume 65, Number 233)
pages = 75771-75816
publisher = U.S. Department of Transportation, Federal Motor Carrier Safety Administration
date = December 42000
accessdate = 2007-07-30 ] As a result, US 26 is closed to hazardous material transport between I-405 and Oregon Route 217.

The tunnels are located nearly at the bottom of a hill where the road gradient averages 6.5% over 2.25 mi (3.6 km). Close to the east portals is a 130 foot (40 m) tunnel underpass carrying SW 18th Avenue. Just outside the west portals is a 650 foot (200 m) tunnel under the lanes which carries eastbound Canyon Road [Before the Sunset Highway was built, the two lane Canyon Road extended into Goose Hollow.Street signs near the Vista Bridge indicate the junction of SW Jefferson Street and SW Canyon Road.] from the exit ramp into Goose Hollow. The Robertson Tunnel for MAX Light Rail is underground approximately 800 feet (250 m) to the west.

See also

* List of tunnels in the United States
* List of tunnels by location

References

External links

* [http://www.tripcheck.com/popups/Cam.asp?camera=529&curRegion=16 Oregon Department of Transportation live camera]