Sunday, March 03, 2013

Metro versus Highway costs

There's been a lot of discussion about transportation funding in the Commonwealth this past month and we saw this interesting discussion of the benefits of Metro to our area. 
WMATA PlanItMetro blog describes how I-395 North would have traffic jams extending 13 miles in the morning without the benefit of the Yellow Line Metro service: 
Metrorail’s Yellow Line crosses the Potomac from Virginia into DC parallel to I-395′s 14th Street Bridge. Both the rail and highway bridges move large numbers of people into the regional core during the morning rush hour. Between the two inbound spans, the 14th Street Bridge has six lanes. The Yellow Line provides the equivalent of three additional lanes. This math is pretty simple: one lane of freeway traffic can move about 2,420 people per hour (2,200 vehicles per hour times an average auto occupancy of 1.1 people per car) and the Yellow Line moves around 7,400 passengers from Pentagon to L’Enfant Plaza during the peak AM hour. Another way to see it is that the Yellow Line removes 6,700 (7,400 pax / 1.1 pax per car) cars from the road.
We repeat for emphasis: "The Yellow Line provides the equivalent of three additional lanes."

So how much is that worth? It turns out that VDOT is just about to add a fourth lane to a portion of I-395. The project is described in the Council of Governments Long-Range Transportation Plan:

  1. Widen I-395, Shirley Memorial Highway – Southbound from Duke St. to Edsall Rd.
Click map for larger image.
Add a fourth lane to southbound I-395 between Duke St. and Edsall Rd.
1.5 miles
$58.5 million

See the CLRP project description form for more information.

That would be about $39 million per mile of highway. 3 more lanes for 13 miles would equate to over $1.5 billion!

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