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You have claimed that the reversible HOV lanes are not cost effective, compared to rail. You have not shown this.

Where did I compare directly to rail?

Look, the facts are these: highways are low capacity arteries. You get a free-flow throughput of about 1,800 vehicles per lane per direction. With the HOV lanes in your direction that gives you 5 lanes inbound or outbound on most of 395. 5 lanes*1,800vph*1.2persons per car = a throughput of just under 11,000 persons per hour, per direction. Even if slugging raised the average occupancy to, say, 1.5 (which is a huge increase) you're talking about a capacity of ~13,500 pphpd (persons per hour, per direction).

Now, take Metro. Metro considers a car with 125 people to be full (even though you could squeeze more on), thus an 8 car train's capacity is about 1,000 people. Running a modest 10 trains per hour (a train every 6 minutes) yields you a capacity of 10,000 pphpd. Run the trains at the max capacity of most subway systems (more like a train every two minutes) and you're talking about max capacities of 30,000 pphpd.

See this PDF - Page 3 - for a nice comparison:

http://stuff.mit.edu/afs/athena/course/11/11.951/oldstuff/albacete/Other_Documents/Europe%20Transport%20Conference/local_public_transport/public_transport_m1679.pdf

Once you get to a certain point on a highway, you're just not going top squeeze any more juice from the orange. Adding things like HOV lanes are relatively high cost investments that add little to the overall capacity when compared against rapid transit.

by Alex B. on Jun 13, 2012 3:20 pm • link • report