- It is 10-kilometer long (a bit over 6 miles)
- It is a round-trip
- To satisfy demand, you need to have a frequency of 4 buses per hour (capacity for a transit line = frequency of the vehicles times the capacity of each vehicle)
- You can expect an average speed of 15 km/h (around 10 mph)
- You have 400 riders who will take the bus
- We will neglect the issue of layover for clarity, buses that end the route can start again just as fast as they arrive
|Each line represents a bus going from the start of the route (0) to the end (10)|
- 3 buses, so initial capital cost of 1 200 000$
- 7,25 vehicle-hours of running time, so 1 100$ operating cost
- To pay back operating costs, each ticket must cost 2,75$
- The capital cost is now 33% higher, to 1 600 000$
- The operating cost is 22% higher at 1 350$
- To pay back operating costs, each ticket must cost 3,38$ if all 400 riders stick to the bus...
- ...but if the slow speed convinces say 50 of them to stop taking the bus, the cost per remaining rider is 3,86$, 40% higher than previously
Overall, in this case, the cost of the transit service in relation to speed can be represented the following way:
|Cost per passenger of transit service depending on whether we suppose ridership to be static (always 400 during peak hours) or dynamic (4% gain or loss per 1 km/h difference in average speed)|
Case study: streetcars
Some sources mention an average speed of 10 to 12 miles per hour (16 to 20 km/h) for streetcars in the US in the early 20th century (Source and source). Though it doesn't look that fast, take into account that the average speed of buses in New York City nowadays is 7,5 mph (12 km/h). In Montréal too, the average speed of buses in Montréal during the peak hours (when most people take transit) is about 12-13 km/h, around 7-8 mph. Despite nearly 100 years of technological advancement, transit is slower than back then.
Though data is scarce on the early 20th century (at least as far as I can find on the internet), most sources mention growing congestion as more and more cars came on the road. Traffic lights and stop signs started appearing in the 1910s and 1920s to deal with the higher vehicular traffic. These signalizations, though they ordered traffic, also had the effect (and still do) of causing delays on arterial roads. Even a well-programmed traffic light at a relatively little used intersection will frequently incur around 10-20 seconds of delay on average to cars passing through. So if you have one traffic light every 500 meters (around a third of a mile) on a 10-kilometer trip (6-mile), you will likely lose 3 to 6 minutes at traffic lights. So if you used to be able to do that length at an average speed of 20 km/h (12 mph), now you could have seen your speed actually fall down to 16-18 km/h (10-11 mph).
I imagine visually this is how traffic should have evolved:
|Streetcars with mainly horse-drawn carriages and plenty of pedestrians (not shown), traffic is generally fluid due to few vehicles and low speeds of vehicles, allowing them to easily negotiate intersections|
|Cars become much more common, now there is friction at intersections and police directing traffic|
|Finally, we start adding signals to intersections|
In old sources, often streetcars were blamed for congestion, due to the windshield perspective of those who used to have access to the media and the attention of the powerful. This is for a simple reason: most streetcars actually had tracks in the center of the street, in the left lane, the fast lane. How did passengers board? Well, at first, passengers waited in the street, forcing cars to slow down not to hit them. As traffic became more ordered, here is how it worked, and still works in Toronto:
Is it any wonder then that car drivers seethed at the sight of streetcars that blocked two lanes of cars when allowing passengers to board or alight? And why car drivers were so receptive to arguments for replacing streetcars by buses?
So, anyway, some posts back, I made a graph about the average speed of transit lines depending on how many stops they had to make and their maximum speed. I will re-use this to illustrate the effect of congestion on streetcar lines.
First, the original situation where streetcars largely had to stop only for passengers and faced little to no congestion to slow them down.
|Initial situation, where streetcars only had to stop for passengers and faced no congestion|
|Now, after cars started congesting city streets and imposed traffic lights and stop signs, streetcars stop more often and go slower|
More importantly, this thought experiment reveals that streetcars, far from causing congestion, were actually a VICTIM of the congestion caused by cars. Car congestion increased transit operating costs and lowered their average speed, making them more expensive and less attractive at the same time.
Streetcar companies, that used to be profitable, started requiring influx of public funds to stay afloat, many were bought by cities. Even when the streetcars were replaced by buses, it didn't help matters, and transit companies, now public, often require up to 70% of funds to come from public money and not fares. A result of three factors:
- Less ridership
- More expensive operations as the lines are now slower
- Transit as welfare policy in cities now built around motorized transport
Lesson for future surface transitThe lesson we can take from these facts and what happened to streetcars should be clear: in highly motorized cities, transit requires reserved right-of-way to protect itself from congestion. In some small cities, maybe they don't need it yet, but if they plan on growing, they should do it as quickly as they can, because when congestion becomes common, taking any space away from cars will be more and more politically contentious.
This is a lesson I think developing cities especially need to take to heart. As people start being able to afford motorbikes or cars, they risk overwhelming streets and causing monstrous congestion. When this happens, bus services running in mixed traffic will suffer most, because the speed reduction will result in transit companies either requiring massive subsidies to keep running, or going bankrupt, thus pushing people into private motorized transport. Even worse, those who will not be able to afford motorized transport will have to walk in congested roads where they are likely to be hit, wounded or killed. Congestion may also choke cities and lead to good jobs and wealthy residents fleeing to sprawl, copying the North American mode of development that left desperate poor people in urban areas.
Considering this, I think developing cities need to implement transit-only lanes and BRT quickly, because it will only get harder to implement as more and more people get motorized. BRT exists here to essentially protect buses from the congestion that cars and motorbikes create and safeguard transit riders' access to an acceptably fast and safe form of transport. If buses are left in mixed traffic, transit use will simply evaporate over time.
For developed cities, modern tramways on their own ROW or even better, grade-separated LRTs and subways, should be preferable, because their lower labor requirement means they will cost less in the long-term and be more attractive to people who already have cars. But even bus lanes to go around congestion will do a lot of good in order to provide for more affordable transit that is more attractive to people.
Eventually, developing countries should also invest in rail, I think, for as they become richer, labor will become more expensive and the buses that used to be cheap will become more and more expensive. Rail can avoid that issue, and also provide for much higher capacity for less space.