Labels

9-line access access management access point accessibility ADA air quality alignment amenity antiplanner atlanta BART BID bike Blogs boston branded bus branded buses brookings brt bus Bus Rapid Transit BYU capacity car pool cars central link Centrality certification commuter rail condo congestion congestion pricing connections consistency coverage crossings CRT cycling DART dedicated dedicated right of way density denver depreciation developers development economics efficiency Envision Utah equity eugene exclusive extension FAQ favela Federal Funding Flex Bus florida free fare zone freeways Frequent Transit Network frontrunner frontunner Gallivan garden cities gas prices geotagging goat Google grade-separation Granary District growth headway heavy rail hedonic High Speed Rail history housing housing affordability housing bubble housing prices HOV income infill innovative intersections intensity ITS junk science LA land use LEED legacy city light rail linear park location LRT lyft M/ART malls mapping maps metrics metro MetroRail missoula mixed mixed traffic mixed-traffic mobile mode choice Mode Share multi-family MXD neighborhood networks news NIMBY office online op-ed open letter Operations parking parking meters peak travel pedestrian environment phasing Photomorphing planning Portland property property values Provo proximity quality_transit rail railvolution rant rapid rapid transit RDA real estate redevelopment reliability research retail Ridership ridesharing right of way roadway network ROW salt lake city san diego schedule schedule span seattle separated shuttle silver line single family SLC SLC transit master plan slums smartphone snow sprawl standing stop spacing streetcar streetscape streetscaping subdivision subsidy Sugarhouse Sugarhouse Streetcar Tacoma taxi technology tenure termini time-separation TOD townhouse traffic signal tram transit transit networks transit oriented development Transit Planning transponder transportation travel time TRAX trip planning trolley tunnel uber university of utah urban design urban economics urban land UTA UTA 2 Go Trip Planner utah Utah County Utah Transit Authority vmt walking distance web welfare transit Westside Connector WFRC wheelchairs zoning

Tuesday, October 12, 2010

Capacity Equilibrium

In California, in San Francisco, they replaced a 3-person carpool lane with a 2-person carpool lane, because it was vacant most of the time. Makes sense, right? Lower the limit, more people will carpool, and the lane will be filled up with carpoolers!

This is exactly what happened on the first week. One the second week, all the new carpoolers realized that the carpool lane was just as congested as a regular traffic lane, so there was really no point in carpooling anyway. And fewer people carpooled until the lane reached some kind of equilibrium, where it made sense for people to carpool again.

So, no problem, right?

Wrong. One lane of 2-person carpoolers is worth as much lane capacity as two lanes for regular cars. One lane of three person carpools is worth three lanes of single-rider cars. Switching from a 3-person to a 2-person carpool effectively sacrifices a lane.