Dick Spotswood: Cost analysis of cyclist proposals must pencil out

There’s no shortage of enthusiasm for expensive public projects. Many of them would be fine amenities if their cost survives a costs-and-benefit ratio analysis. If every dollar spent returns, say, $3 in benefits, the expenditure of public money has positive net value. Alternatively, if for every dollar, 50 cents is returned in value, the project is a waste of taxpayers’ money.

A project that should have undergone that test is the San Rafael-Richmond Bridge upper deck bike and pedestrian lane. The dollar costs are in the tens of millions when including the addition of a bike lane to the approaches on the Contra Costa County side of the bridge. That effort included moving a retaining wall on the south side of Interstate 580 which Caltrans improbably claimed was a highway improvement.

In addition to out-of-pocket expenses are the bikeway’s social costs. In 2025 that included quality hours lost by 38,000 westbound vehicle travelers. That’s inevitable when they encounter traffic congestion where the bridge’s as-built three traffic lanes are forced into two.

This congestion hasn’t diminished even though Caltrans now limits bikes, and pedestrian use, to weekends. The “third lane” remains closed to traffic. It’s now reserved for disabled vehicle pull-offs and bridge maintenance. On the other side of the ledger are those who benefited from the lane’s closure. On average 2025 weekdays there were 132 bike trips and 24 pedestrian crossings. That grew to 347 one-way trips on bicycles plus 47 hikers on weekends.

That’s a pathetic cost-benefit ratio. If those numbers were known before the Richmond Bridge’s bike lane was more than a cyclist’s dream, public outrage would have derailed the fiasco.

Now there’s a renewed push to reconstruct the old Alto rail tunnel between Corte Madera and Mill Valley. The single track bore saw electric passenger railcars until 1940. The last freight train linking Sausalito with the Northwestern Pacific Railroad’s mainline in San Rafael rumbled through the Alto Tunnel in 1971.

For safety’s sake and to keep the unhoused out, Alto Tunnel was sealed in 1979 at portals near Corte Madera’s Chapman Meadows neighborhood and in Mill Valley’s Scott Valley. In 1981 a disastrous fire of unknown origin caused the tunnel to collapse near its Mill Valley portal. With concrete and pea gravel sealing the northern end of the tunnel and debris from the collapse, Alto Tunnel was effectively destroyed.

For decades Marin’s ever-growing cycling community dreamed that the rail tunnel could be reconstructed and opened to bikes and walkers. It’s true, reconstructing Alto Tunnel would be a fine amenity linking Sausalito to Sonoma via the popular North-South Greenway.

The question is whether reopening Alto Tunnel could pass a cost-benefit analysis? There’s no harm in learning what it will cost in 2026 dollars.

In 2017, Marin’s Department of Public Works commissioned a study which concluded that the tab would be $60 million. Opponents of reconstructing the tunnel who mostly live along the old railroad right-of-way near its Corte Madera and Mill Valley portals contend the cost including acquiring essential easements will be at least $100 million.

Aside from determining its cost, no decision on rebuilding Alto Tunnel should take place without a cost-benefit analysis. With the San Rafael-Richmond Bridge bikeway, Marinites and Contra Costa commuters learned the hard way what happens when that step is bypassed.

The reality is that if rebuilding the Alto Tunnel costs “only” $100 million and on average high-use weekend days, say, 1,500 cyclists and hikers use the bore, it will never provide social benefits worth $100 million.

Regardless of whether tunnel reconstruction grants originate from the County of Marin, the State of California or Uncle Sam, it’s all our money. We need to first ask: Is this scheme the highest and best use of $100 million tax dollars? The hard truth is that it does not.

Columnist Dick Spotswood of Mill Valley writes on local issues Sundays and Wednesdays. Email him at spotswood@comcast.net.