which bridge: a wee geographic project

[calimac]

While trying out the automated route function of an automated road atlas to see what it recommends on some trips I'm planning, it occurred to me that while automated route-planning is inept in many ways, it could tell me with little fuss which of the various bridges across San Francisco Bay is the shortest route between two places on opposite sides. So I tested it out on various pairs of inner Bay communities and got this little table here, with the selected Marin & Peninsula cities in rows and the East Bay cities in columns:

	Vallejo	Crockett Rodeo Hercules	Pinole San Pablo Richmond El Cerrito Albany	Berkeley	Oakland	Alameda	San Leandro	San Lorenzo Hayward Castro Valley	Union City	Newark	Fremont	Milpitas	San Jose
Novato	37	Carquinez	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond
San Rafael	37	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond
Greenbrae	Richmond/Carquinez	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond
Larkspur Corte Madera	Richmond/Carquinez	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Richmond	Golden Gate
Mill Valley Tiburon	Richmond/Carquinez	Richmond	Richmond	Richmond	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate	Golden Gate
Sausalito	Richmond/Carquinez	Richmond	Richmond	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate/Bay	Golden Gate	Golden Gate
San Francisco	Bay/Carquinez	Bay	Bay	Bay	Bay	Bay	Bay	Bay	Bay	Bay	Bay
Daly City	Bay/Carquinez	Bay	Bay	Bay	Bay	Bay	Bay	Bay	San Mateo	Dumbarton	Dumbarton
Brisbane South S.F.	Bay/Carquinez	Bay	Bay	Bay	Bay	Bay	Bay	San Mateo	San Mateo	Dumbarton	Dumbarton
San Bruno Millbrae Burlingame	Bay/Carquinez	Bay	Bay	Bay	Bay	Bay	San Mateo	San Mateo	San Mateo	Dumbarton	Dumbarton
San Mateo	Bay/Carquinez	Bay	Bay	Bay	Bay	San Mateo	San Mateo	San Mateo	San Mateo	Dumbarton	Dumbarton
Foster City	Bay/Carquinez	Bay	Bay	Bay	San Mateo	San Mateo	San Mateo	San Mateo	San Mateo	Dumbarton	Dumbarton
Belmont San Carlos Redwood City	Bay/Carquinez	Bay	Bay	Bay	San Mateo	San Mateo	San Mateo	San Mateo	Dumbarton	Dumbarton	Dumbarton
Atherton	Bay/Carquinez	Bay	Bay	Bay	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton
Menlo Park East Palo Alto Palo Alto Los Altos Mtn View	Dumbarton/Carquinez	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton
Sunnyvale Cupertino	Dumbarton/Carquinez	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	237/880
Saratoga	Dumbarton/Carquinez	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	Dumbarton	880
Santa Clara Campbell Los Gatos Milpitas San Jose	880/Carquinez	880	880	880	880	880	880	880	880	880	880

Of course this isn't always the best route, due to traffic, or a preference in taking the free direction on the Richmond bridge over the high-toll direction on the Golden Gate, or whatever. But these are the shortest routes as measured from whatever DeLorme considers the center of town. Milpitas and San Jose are also included in the East Bay listing as the only Peninsula towns for which the Golden Gate Bridge isn't always the shortest route to Marin.

I'd long suspected that the San Mateo bridge is good only for a relatively small set of destinations on each end, and now I confirm that's so. I also find that, living at the far west end of San Jose, I'm actually in a place where the Dumbarton Bridge would be a shorter path to the East Bay than 880, which I normally take.