Optimizing bus routes to improve traffic flow
Friday, June 20th, 2008
Problem
Everyone knows that traffic sucks in LA - too many cars, and too few public transportation options. There are currently a few proposals to alleviate traffic woes and prepare LA for growth:
- Increase the Metro coverage area with new lines (Los Angeles’ subway system. Yes, LA has a subway system)
- Convert more streets to one-way streets, e.g. Olympic, Pico. This improves flow by increasing the number of lanes of flow traffic and reducing the opposite-direction turning lanes. Basically, you can get rid of the middle turning lane and assign it to one-way non-interrupted flow traffic.
Both of these options are a few years out. By and large, LA’s current public transportation strategy revolves around bus routes. This is a double-edge sword. While it does provide public transport, it slows down already congested streets because the buses are big and slow, make frequent stops, and often have to cross multiple lanes of traffic for turns. In the general sense, public transportation is an attempt to improve city-wide travel efficiency, mainly by reducing traffic. In LA’s case, the bus strategy can often aggravate traffic.
Solution
So the question is, how can we keep the buses without having them harm existing traffic flow? I think part of the answer is optimizing existing bus routes. It’s pretty clear to me that LA bus routes are inefficient. There are too many buses with too few people riding them. It is a gross inefficiency to have the largest vehicles on the road carrying the least number of passengers. I frequently see double-car buses carrying only a handful of people. This is like having 4 SUVs, each with just one rider.
I think LA should introduce passenger vans for many routes, or introduce some type of mini-bus. Let’s get rid of the big, ponderous, awkwardly large buses and replace them with nimbler, faster rides. This has several advantages:
- increased fulfillment percentage: In an ideal world, buses are full or nearly full a majority of the time
- faster vehicles: Even if the smaller vehicles have to make the same stops, smaller vehicles have better acceleration and get to their top speed quicker
- environmentally friendly: air-conditioning large, unoccupied spaces wastes energy and this exactly what large buses do
Implementation
The main hurdle with a mini-bus or optimized bus strategy is that it’s hard (read: costly) to know what routes are inefficient. So, the LA bus system takes the easy way out and they just use the large capacity buses for all routes. But there are a few simple techniques we could use today without having to compute the inefficiency weight on each route.
- On non-peak hours, have all routes only use the mini-buses. This one is easy - buses on non-peak hours have very few people on them, just start using the smaller buses.
- During peak hours, every other bus (or every third bus) is a mini-bus.
- Poll the bus drivers to figure out which routes could benefit from a bus size reduction. I think the bus drivers opinions would rival any computer model - they’ll have an intuition about the congestion because they’ve driven the route many times before.
Conclusion
There’s no reason why we have to wait until the new subway lines before we can reduce traffic in LA. Buses are a big pain in the butt on major streets like Wilshire and anything we can do to reduce the number of buses or make them smaller would go a long way towards mitigating congestion.
