It’s not how far out in the future Sound Transit’s proposal is that’s so startling. It's Sound Transit’s vision of the future that's so startling.  

“The assumptions they’re making are for a 1940 transportation system not a 2040 transportation system,” Stanford instructor Tony Seba told me yesterday. Seba, the keynote speaker at last year’s California Transit Association conference where he gave a TED-talk style presentation on driverless cars, is the author of Clean Disruption of Energy and Transportation.

Antsy myself about the big parking expenditures in the ST3 proposal—roughly $700 million so far (in a $20 billion 2014 capital budget ) for about 10,000 new parking spaces—I ran the numbers by Seba. (I crunched the numbers last week and found about $500 million in parking expenditures while noting that some parking costs were TBA in ST's documents; ST has since updated the figures for me to about $661 million, with other parking costs still TBA.)

Yes, Seba's a TED talk type—so feel free to quibble with his vision of the driverless car future (he says driverless cars will be shuttling people to and from work and then, rather than parking, the super smart car will stay on the road to cater to the next person).

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But his research shows that the combination of driverless cars and car sharing are going make “the need for parking spaces obsolete.”

For starters, Seba figures the cost of owing a car will be about 10 times greater than the cost of not owning a car by around 2030. Noting that today’s data shows that cars are parked about 96 percent of the time, Seba says:

“Utilization is going to go up 60 to 80 percent—cars will be driving around the all the time instead of being parked all the time. When you have cars driving around all the time, the cost per mile of not owning a car is going to be 10 times cheaper than the cost of owning a car. People are going to stop owning cars because it’s going to be economically the right thing to do.”

His math: Today we pay about a dollar per mile for car ownership, which Seba puts at $12,000 a year. He contrasts that to a $1,200 price tag for relying on drivereless car-on- demand car sharing. “Who would say ‘I’d rather pay $11,000 more for the privilege of owning a car that I keep parked 96 percent of the time?’ It doesn’t make any sense.”  

Seba estimates that this model of shared driverless car fleets will shrink the fleet of cars on the road by about 80 percent. “The big picture,” he says, “is that 80 percent or so of parking spaces are going to be obsolete by 2030, certainly by 2040” when Sound Transit Three comes fully online.

As for ST3 specifically, Seba said: “If you’re building for 2040, it doesn’t make sense to build that many parking spaces or any parking spaces at all because they’re using assumptions from the past not the assumptions for the transportation system of the future which is going to be mobility on demand.”

Seba notes that Seattle has about one million free and paid parking spaces today. And by his math, 800,000  parking spaces are going to be empty or obsolete by 2030. “That means if you’re building new parking spaces, those are going to be obsolete, especially if your assuming you’re going to build them by 2040.”

He also notes that at $70,000 a parking spot (the $700 million expenditure on about 10,000 new spaces)—tax payers would be subsidizing cars for about twice the current value of a new car.

“Even if you assume that we are going to need parking,” he concludes, “$70,000 per parking space—that is twice the cost of the median new car in America. Is it really fair for the taxpayer to subsidize parking spaces? Why aren’t we asking the question: Do we really want to subsidize parking at nearly twice as much as the cost of the car?”