Monday, October 13, 2008

Tappan Zee: Sorting out the factors

If I was a real math whiz you'd be seeing some purty factor analysis of this, but I created a spreadsheet with a chart that lets us see the effects of various Tappan Zee build scenarios on relative capacity, which is hopefully a decent approximation for relative value.

It's been really hard to pick out from the documents on the State DOT's web site, but here's the raw data I used:

1999 survey data (Alternatives Analysis Chapter 4, p. 6)
Percent of people crossing by private car98 %
Percent of people crossing by bus02 %
Vehicles per lane per hour (Level 1 Screening Criteria, p. 18)
Passengers per hour by transit mode (Transit Mode Selection Report Chapter 5, p. 16)
Alt. 3B (BRT) Planned2100
Alt. 4D (BRT+CRT) Planned6800
Alt. 3B Max9000
Alt. 4D Max39000

The current mode share on the bridge is 98% private cars. The scenarios with any form of Bus Rapid Transit would bring it down to 70-80%. Commuter rail - or maximizing use of the bus lane to 9,000 passengers per hour) - would bring it to 40-55%. Maximizing use of the commuter rail (i.e. 39,000 passengers per hour) would bring it all the way down to 12-16%.

1 comment:

BruceMcF said...

How hard would it be to suspend an aerobus system from the bridge? While that is light rail rather than mass transit, it would seem to avoid contention with BRT and car lanes.