Elon Musk had a curious series of tweets over the weekend about how he was going to get involved in tunnel boring.  Why would a man who dreams of Mars want to get into such a “boring” business?  I’m speculating on what might be Musk’s motives here, but here’s an intriguing possibility.  Networks of tunnels, if they were built to electric-vehicle-only specifications, could be the “killer app” that could lead the masses to finally ditch the internal combustion engine and switch over to electric vehicles (the main product of Musk’s more well known company, Tesla Motors.)

Despite the high-profile breakdown of  the “Big Bertha” tunnel boring machine underneath Seattle, the cost of building tunnels is actually decreasing due to advances in tunnel boring machine technology.   Furthermore, a tunnel built for the exclusive use of electric vehicles would be cheaper to build, operate, and maintain than one built to accommodate gas powered vehicles.  Since electric vehicles have no exhaust, the specifications for ventilation equipment would be a less demanding for an electric vehicle-only tunnel,* and it would cost less to operate over time.

Built underneath the hillsides of a city like Los Angeles or Cincinnati, these tunnels would allow electric vehicle owners to bypass the traffic, stoplights, and other “friction” of the streets above.  At least before the electric vehicle market matures and the “induced demand” phenomenon kicks in, one would have the sense of traveling between one tunnel endpoint to another in a Super Mario Brothers warp-zone-like fashion.  The right to use the tunnels would give consumers a reason to purchase electric vehicles beyond environmental altruism or the always-changing system of tax credits from the government.

Electric vehicle exclusivity of the tunnels could be maintained by installing red-light style cameras that could get the license plate of any non-electric vehicle attempting to use the tunnels, to be followed up with a hefty fine delivered in the mail.  (The ventilation system would still have to be large enough to handle the fumes from one or two scofflaws at a time.  Additionally, it could be built robustly enough to accommodate the occasional  gasoline-powered emergency vehicle.)

Since the market share of electric vehicles is at such a low level today, and they are mostly available only to the well-to-do, tunnel construction could be justified by accommodation of mass transit.  Electric buses (or the occasional streetcar) could have exclusive, dedicated lanes in the tunnels alongside lanes for private vehicles. The dual-use nature of the tunnels could give the concept more political support than if the tunnels were for either mass transit or private vehicles alone. Tunnel construction costs could also be offset by encouraging Transit-Oriented Development near the portals of the tunnel to grow the tax base.

The widespread adoption of electric vehicles in a city like Cincinnati, where the smog gets trapped in overhead for days at a time by our hills, would have positive ripple effects in our quality of life, improving our health and economic competitiveness. Currently, Cincinnati consistently ranks high on lists of places with the worst air quality in the United States.  As CO2 emission intensity from power plants and industry fall, auto exhaust remains a stubborn source of not only CO2 emissions but other nasty particulate pollution.

*NOTE: Another factor in tunnel ventilation design is the emergency management of smoke and fumes in case of fire inside of the tunnel.  Electric-vehicle-only tunnels would still of course have to design for this, so I would need a subject matter expert to determine how significant the up-front equipment savings would be if tunnels were designed to be electric-vehicle-only.