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Wednesday, February 3, 2010

Reducing congestion on our roads

Yesterday I was driving on a mercifully un-congested road, listening to KUOW's The Conversation, and caught a segment about the proposed 520 bridge replacement. Briefly, the proposal is for a six-lane bridge, with two regular and one HOV lane in either direction. The 520 bridge currently has no HOV lanes, which makes the HOV lanes on the eastern portion of 520 kind of useless because they do nothing to alleviate the choke-point that is the bridge.

The crux of the issue under discussion yesterday is that while this proposal has been in the works for some time, a "Citizens Group" that happens to include Seattle Mayor Mike McGinn and House Speaker Frank Chopp is saying what the bridge really needs are dedicated mass transit lanes instead. Governor Gregoire dislikes this change because it would delay the bridge replacement by up to two years, which she says isn't in the interests of public safety.

What I was really struck by in listening to people calling in to the program, either yammering for or against the change, was the level of blithe misinformation about mass transit that seems to be informing a lot of people's thinking.

One caller in particular captured this ill-informed viewpoint perfectly. She was against the transit lane proposal because she didn't want to crowd the cars into the remaining two regular lanes. And I quote: "Mass transit lanes are not going to be the most efficient use of a travel lane." She then went on to say that she "has a strong desire for mass transit" in the long term, but that for now she just couldn't see not making the most efficient use of the lanes we have.

Which would make sense except for one thing: She's flat-out wrong in her assessment of lane efficiency. Mass transit actually is the most efficient use of a lane. Period.

One bus, because of its enormous capacity to hold people, moves more people per minute down each mile of freeway than an equivalent carrying capacity of cars does. True, there's not a bus going by every twenty seconds, but because that bus carries so many people, there doesn't need to be.

The bus is a win for everybody. It moves its passengers more efficiently than they could move themselves in cars, and by getting those passengers' cars off the road, it reduces congestion for the luddites who are still in their single-occupancy vehicles.

Light rail is even more efficient because trains don't share the same physical space as cars. A light rail lane would, for obvious safety reasons, probably have to be walled off from regular traffic lanes, which is a good thing all around. The train can zip across the bridge at full speed, carrying the equivalent of hundreds of cars worth of people, in less time than a single car can cross the bridge.

This is what people don't get. Mass transit really is more efficient than private car fleets. It's counter-intuitive, but it's true. We see the freeway filled with cars, and when things are moving well it seems like the cars are zipping right by and thus we have the perception that a lot of people must be getting where they're going pretty quickly.

But the rider-density of all those cars is so low, even with carpooling, that the car fleet just can't compete with mass transit. When traffic is flowing well, you might see twenty cars per minute pass by any given point. On the generous assumption that one quarter of those cars have a passenger, that's 25 people per minute per lane.

A dedicated mass transit lane carrying busses, even if only one bus per minute passed by your observation point, can easily carry 50 or more people. And with a bus fleet collecting riders from the entire Bellevue/Redmond/Kirkland area, it's not difficult to imagine meeting that one bus per minute metric. A dedicated mass transit lane can out-perform even two regular traffic lanes, without breaking a sweat.

This is what people fail to understand. Busses and light rail are much more efficient than cars. They always will be, unless you can find a way to fit fifty people into a Toyota.

The 520 bridge replacement needs dedicated mass transit lanes in order to serve the region's short term AND long term needs. It's the only way we're ever going to really reduce congestion, on 520 or anywhere else.


Blogger Stealth said...

You are missing a very important detail here:

If HOV lanes were on the bridge as well as on the freeway and more carpools were the result, You would have to subtract the emissions from people not driving alone and add that to your equation.

For example:

Let's say you have a bus with 30 people on it.
You would need 10 vehicles with 3 people each to move the same amount of people. Now, I know what you're thinking: "1 bus is WAY better for the environment than 10 cars!" and you would be correct. However, what you are forgetting is there are now 20 less cars on the road because of the carpooling. And reducing the number of cars on the road is the whole point of all this, isn't it?

I want to see the scientific study that proves people will not carpool more if there are HOV lanes on the bridge, or if they do that it will still be worse for the environment than a light rail only option.

The other thing you are forgetting is people do not take the bus because there is an HOV lane on their route. People carpool or take the bus because it is FASTER than the alternative. You can't MAKE people take the light rail by taking away the HOV lane on the bridge, they will ONLY use the light rail if it is faster/cheaper/better than driving. Some people don't even care; they are going to drive no matter what and you can't change that. If you add an HOV lane to the bridge MORE people will carpool because it is minimal effort and it is faster than sitting in the general use lanes.

I don't have a car, but I used to commute over the 520 and I would get a ride home free from a co-worker because it was an incentive for him to get to the bridge faster with 2 other people in the car.

Also, this is not just about reducing congestion. If it were, then all we need to do is add 10 lanes to every highway and teach people that if you drive slow, stay to the right and let faster traffic pass you on the left.

February 4, 2010 11:23 AM  

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