Transit Calculations

I crossed the I-90 bridge earlier today while the express lanes were empty for changing directions.  This is where the EAST LINK rails will be placed.  There's a lot of bridge lane that's going to be used for this.  It will be a net reduction in the capacity of the road, even if they share it with buses.

Everything here is in meters.  PPHPD is passengers per hour per direction, per lane.   So 6 freeway lanes, three each way, each operating at maximum vehicle capacity (1800/hr/lane) with an average 1.2 passegers per vehicle, can carry 12960 passengers.  two light rail lanes, one each way, 5 minutes headway with 200 passenger vehicles, can carry 4800 vehicles.   you can run closer than 5 minutes apart on the bridge, but because there are stations at the end of the line and on mercer island, you can't actually do it.  Central Link today runs at 7.5 minute headway during rush hour, so the actual PPHPD is 1600.  Actual Link ridership for the whole 17 mile, two way route is about 32K/day

Estimates for PRT are for a first system, one way. the 2.4 mile (1.2 2way) Heathrow ULTra system cost about $45M to install. More installations will drive costs down.  Installations in denser cities will cost a little more (but not as much as heavier systems).  The cheapest LRTs installed in the last few years cost about $50M/2 way mile.  the most expensive are over $200M

Width Height Top spd Avg spd PPHPD $M/km 3.6 5 97 97 2160 10 12 foot freeway lane, 60 mph, 2 second headway, 1.2 pass/veh 3.6 5 97 8 500 10 12 foot freeway lane, stop and go traffic 3.6 5 40 13 1000 7 12 foot urban lane, 1 minute traffic light every 400 m 4 5 97 36 2400 30 200 pssngr LRT, 5 min headway 2 minute stop 3000m 4 4 97 97 2400 30 200 pssngr LRT, 5 min headway, nonstop 4 5 97 36 600 10 50 pssngr bus, 5 min headway, 2 minut stop 3000m 5 5 97 36 12000 140 1000 pssngr subway, 5 min headway, 2 minute stop 3000m 2 3 40 38 360 20 low capacity PRT, eg ULTra, 15 sec headway, 1.5 pass/veh 2 3 60 57 5400 20 high capacity PRT, eg Skyweb Express, 1 sec headway, 1.5 pass