Super-Highway on Viaduct to Break San Rafael Bottleneck
by Robert L. Harrison
The title introducing this article comes from the July 1940 issue of the California Highways and Public Works magazine by Caltrans Bridge Engineer F. W. Panhorst. He was reporting on the initial construction of the Highway 101 viaduct over five main east-west streets in San Rafael. Expectations were high that the viaduct would to do much to relieve Marin County traffic congestion.
In the same magazine’s July 1941 issue T. E. Ferneau, Caltrans Resident Engineer, described the history of traffic congestion in Marin following the opening of the Golden Gate Bridge. His description of conditions 80 years ago would be familiar to today’s driver: “Constant turmoil has been the record of highway transportation through Marin County. Elimination of one point of congestion has only accentuated a bottleneck at some other location with highway improvements lagging far behind the ever increasing traffic volume.”
Ferneau continued, “Replacement of the shuttling ferry system to San Francisco by the six lane Golden Gate Bridge and the Waldo approach eliminated the ferry bottleneck which in the past caused traffic to back up for miles with a delay period running into hours. But elimination of this traffic block caused immediate and serious congestion in the City of San Rafael….”
Traffic congestion relief in San Rafael was under study by Caltrans as early as 1932. The intersections of Highway 101 with some of the city’s busiest streets were known to cause significant delay for motorists attempting to pass through the city. In 1941 Highway 101 south of the proposed viaduct followed its current alignment as a conventional highway to where it met Irwin Street at grade. From there it was routed north on Irwin to Belle, Grand and Villa Avenues. This circuitous path on narrow city streets required the highway to intersect with Second, Third, Fourth, Fifth and Mission Streets.
In 1939 Highway 101 in San Rafael served an average daily traffic volume of about 13,500 vehicles, three-quarters of which were passing through the city. While only about 8% of today’s traffic load, the 1939 volume caused significant congestion and led Caltrans to study several alternatives to relieve the San Rafael bottleneck. As described by Ferneau, “In keeping with the modern trend toward moving highways away from cities to permit smooth frictionless flow of through traffic and yet serve the needs of local communities, it was planned to remove the highway from the San Rafael city streets in the only manner that seemed feasible for both present and future needs — that is, by an elevated structure that would separate the grades and thus provide the best facilities for separating the through and local traffic. Construction of the viaduct was started in July, 1940.”
The viaduct and its approach roadways were completed in January 1942 at a total cost of $675,000 ($13 million in 2019 dollars). The four-lane 50 feet wide by 2,200 feet long structure itself cost $402,000 in 1942 ($8 million in 2019 dollars). Today the structure carries the four northbound lanes of Highway 101 over the local streets of San Rafael. A four lane parallel viaduct to carry the highway’s southbound traffic was completed at a cost of $3 million in 1970. This year the two viaducts together serve about 160,000 vehicles per day.
The first San Rafael viaduct was considered a major achievement in the effort to provide efficient highways in the Bay Area. It was the north bay’s first limited access freeway. The improved highway was viewed as especially important to the war effort in the 1940s. It did indeed break the San Rafael bottleneck. But new bottlenecks would develop as traffic volumes grew following World War II. Added capacity temporarily resolved each choke point right up to today’s project -now under construction- to widen the highway and relieve the bottleneck at the Novato Narrows.
Originally published at https://annetkent.kontribune.com.
