Saturday, June 21, 2014

BRT versus parking, and making hard choices about street space

What's the most valuable commodity in Cambridge? It isn't water, open space or even housing. In fact, it's street space. Whether given to parked cars, bikes or  pedestrians, it's worth its weight in gold. Therefore, in urban areas like Cambridge, we need to be as efficient as possible about how we use that space. This post is dedicated to talking about the hard choices involved in allocating a given road's surface. For my main example, I'll use Mass Ave south of Porter Square as an example.
Current built environment:
Mass Ave south of Porter currently consists of a separated boulevard with an incredibly thin concrete median. On either side there exists two general use lanes, each roughly twelve feet wide, and one continuous parking lane (no curb bump outs), taking about 8 feet of space. It hosts several bus routes, one, the 77, being a Key Bus Route. There is an incredibly temporal bike lane on the northbound side, and there are 8 foot sidewalks, with frequent obstructions, at the edges.
First, lets see how much space is given to any given mode. I'll use a winner take all system: if a lane is dominated by one type of traffic, I'll give it all to that type. Therefore, general purpose lanes, which are over 90% car, will be counted as car lanes.
Doing the math on street space
8(Sidewalk)+8(Parking)+12(Car)+12(Car) :Median: 12(Car)+12(Car)+4(Bike)+8(Parking)+8(Sidewalk)
So, out of an 84 foot road surface:
64 feet are given to cars,
16 feet are given to pedestrians, with frequent interruptions,
an insignificant 4 feet are grudgingly given to bikers,
and a grand total of 0 feet is given to transit!
To do the percentages, over 75% of the road is given to cars, in the form of parking and travel lanes.
So much for complete streets!
That's a pretty grim picture. Even after being given 64 feet of space on the most valuable road in Cambridge, cars are constantly congested. They move slower than bikes, despite being given 16 times more space! In short, cars are a miserable failure at actually getting people where they need to go in an urban setting.
What we can do:
Therefore, it's time to rethink how we design roads. Lets start by taking two of the car's six lanes on Mass Ave (remember who parking is for), and dedicating it to buses, which have proven themselves much more efficient per square foot of urban space. Then, lets take the parking out, which has a capacity of exactly zero bodies per hour (I will do many additional posts on the folly of on street parking), and replace it with well designed cycletracks. Finally, to decrease speeds and increase safety, lets narrow the two remaining car lanes to 10'6", the minimum allowed for emergency vehicle access, and give the reclaimed three feet to pedestrians in the form of wider sidewalks. Now, we have a real complete street, that gives equal space to every mode.
What it looks like now:
Out of an 84 foot road surface:
24 feet are given to transit,
21 feet are given to cars,
19 feet is granted to pedestrians,
and 12 feet is given to cyclists.
That's a Mass Ave everyone can enjoy.


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