The nearly half-mile-long Alto Tunnel was just one of three bike route improvement plans outlined in a newly released study, part of the Nonmotorized Transportation Pilot Program.
The other two routes are well known to any cyclists who've ridden north of Mill Valley. An existing path over Horse Hill skirts Highway 101 and twisty Camino Alto climbs 450 feet of hill above the tunnel and is a popular segment of weekend training loops for many riders. Improvements on these two routes would cost roughly $5 million each.
But some cyclists shy away from Camino Alto because of its narrow lanes, speeding cars and afternoon traffic jams.
Cyclists have dreamed of reopening the Alto Tunnel as the last barrier to a nearly flat connector between the two towns and a key link to a greenway stretching from the Golden Gate to Cloverdale.
The 16-foot-wide tunnel would link existing bike paths on both sides of the hill. Southern Pacific Railroad sealed the 2,172-foot passageway in 1971, dooming its redwood supports to rot in the stagnant, moist darkness. A cement plug filled 125-feet at one end in 1975 and in 1981 a southern portion collapsed, leaving engineers to guess at the true difficulty of reconstruction.Read more...