By way of Greater Greater Washington, we come across this post which argues that expanding the Metro system would be cheaper than expanding I-66, a major part of the DC area interstate system:
In Arlington for instance, going to eight-car trains on the Orange Line as part of Metro 2025 is like widening I-66 by two lanes. Let’s do the math:
- One lane of highway can move around 2,200 cars per hour, at its theoretical maximum.
- Today, every morning Metrorail runs about 18 trains per hour eastbound on the Orange Line through Arlington, and about a third are scheduled eight-car trains. That’s a train every three minutes, and equates to around 121 rail cars per hour, or 12,060 passengers per hour.
- By 2025 with eight-car trains, Metrorail will be able to run 21, eight-car trains per hour eastbound on the combined Orange and Silver Lines, which equates to 168 cars per hour.
- This means Metro 2025 will bring the line’s capacity to 16,800 riders per hour, or an increase of 4,740 passengers per hour.
- To accommodate 4,740 more people on I-66 at 2,200 cars per hour, 2 people per car, we’d need 4,740 / 2 / 2,200 = 1.1 highway lanes in each direction.
That means we’d need at least two new lanes on I-66 to match the capacity of Metro 2025. In addition, eight-car trains would be cheaper, and would likely move people faster through the corridor.
It will never happen, even though it should: the surrounding areas are unwilling to put money into mass transit beyond what they’ve already done (for reasons I don’t understand, few things cause people to fly off the handle more quickly than traffic policy). As long as Republicans control the House, there’s no chance that mass transit will be given more weight (and money) than cars. Still, it’s worth making the point; we might get lucky…