Kirby: the math
Last weekend, people packed Upper Kirby‘s meeting room to discuss the plan to rebuild Kirby from 59 to San Felipe. The crowd clearly felt that the current plan, which would reduce pedestrian space and require 175 trees to be moved or cut down, is not acceptable. But, as anyone who’s driven on Kirby knows, the existing conditions aren’t very good, either.
Robin and Tory have covered this issue well. I’ll leave the background and the politics to them. But, as elected officials, city engineers, businesses, and the public talk about alternatives, I figure it’s worth reviewing the math.
The public right-of-way on Kirby is 100 feet wide, property line to property line. Right now that’s divided like this:
- 16’6″ feet sidewalk plus trees
- 3 lanes at 9 1/2 feet each
- 10 foot turn lane
- 3 lanes at 9 1/2 feet each
- 16’6″ feet sidewalk plus trees
The Upper Kirby plan has three elements.
- Build a new storm sewer and bury power lines. This is uncontroversial and has no impact on sidewalks or trees.
- Add a median with left turn lanes. Currently, Kirby has a “suicide lane” that allows cars to turn left into side streets or driveways anywhere. That’s convenient, but it’s also dangerous: this stretch of kirby averages 25 mid-block “T-bone” crashes a year where one car broadsides another one that’s turning into a driveway. Adding a median with left turn pockets at side streets would make the street safer. Adding this median requires an extra 4 feet for a double curb with some plantings to separate the left turn pockets from oncoming traffic; a a handful of places where cross streets are far enough apart this would widen into a 14 foot median with trees. The 4 foot median would also create pedestrian refuges at intersections.
- Widen lanes. Kirby’s current traffic lanes are 9 1/2 feet wide. The City of Houston standard for new arterial streets is 11 feet. On this project, city engineers are requiring that this standard be retrofited into the existing street. Nobody is arguing that wider lanes are safer. In fact, they encourage drivers to drive faster, which would increase accident risk. Nor do wide lanes increase traffic capacity, which is limited here by the traffic light cycles. A 9’6″ lane is wide enough to handle any vehicle that uses Kirby; typical cars are less than 6 feet wide; large SUVs are 6’8″ wide; buses and tractor trailers are 8’6″. Narrow lanes don’t make sense on freeways, where traffic is moving at 70. But the speed limit on Kirby is 35. Widening all six lanes from 9’6″ to 11’0″ requires 9 feet.
While the plan combines all three elements, they do not have to be combined. Adding the median and widening lanes takes 13 feet, leaving the sidewalk/tree space on each side at 10 feet. But the median alone only takes 4 feet, leaving 14’6″ and saving most of the trees. And, of course, doing the storm sewer and burying the power lines while keeping the current street configuration leaves the sidewalk/tree space at 16’6″ and saves all the trees.
It’s been the Houston pattern for 50 years to take away trees and pedestrian space in the interest of wider traffic lanes. It hasn’t worked. The streets built to standards are still congested. And, ironically, that’s due in part to the wider lanes. A lot of traffic on a street like Kirby is people driving from one store to the next: from Borders to Whole Foods, from Bed Bath & Beyond to Desert Gallery. If those people would walk a block instead there would be one fewer car on the street. But few will walk on a narrow concrete strip with cars racing by 2 feet away. Kirby is at the beginning of a growth spurt that will result in bigger buildings with retail built up to the sidewalk and parking tucked in behind and stacked above. That will draw more pedestrians out to the street. It would be ironic if, at the same time, the city’s insistence on suburban lane standards makes the sidewalks less friendly.
There’s been a lot of discussion on this in our forums. Widen then with your thoughts.