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 car	98 %
Percent of people crossing by bus	02 %
Vehicles per lane per hour (Level 1 Screening Criteria, p. 18)
Typical	1700
Maximum	1900
Passengers per hour by transit mode (Transit Mode Selection Report Chapter 5, p. 16)
Alt. 3B (BRT) Planned	2100
Alt. 4D (BRT+CRT) Planned	6800
Alt. 3B Max	9000
Alt. 4D Max	39000

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%.