Costs of light rail vs two lane road for cars

You live in a city. Not every road is an eight lane freeway. Most roads in a city are probably two/three lane residential streets. Those kinds of roads are needed, cars are a necessity, albeit an evil necessity, because you can’t simply smother a city in light rail, that’d be too expensive. Or so they say.

Let’s build a ten mile long light rail line. The average U.S costs for the tracks and wiring and what not is $80 million per mile. So it’d be $800 million for ten miles of tracks and stuff. We’d need 11 stations, not ten, because one at each end. Say our stations are a bit on the expensive side, at $50 million each. So $550 million for 11 stations. A light rail vehicle is $4 million, and the Sound Transit trains are four vehicles connected together, so one train would be $16 million. With 90 second headway (the maximum) to enable the most passenger capacity, we’d need 20 trains. 20 trains is $360 million. The average lifespan of a light rail line, trainsets too, is around 30 years. With an annual operating cost of around $30 million including maintenance, the total operating cost over 30 years would be $900 million. So the total cost over 30 years for a 10 mile light rail line would be around $2.6 billion.

Now let’s do the two lane road. An average lane mile is $10 million. So a two lane road is $20 million per mile. A ten mile two lane road is $200 million. In terms of the cost that the city has to pay, that’s it. A road is cheaper than light rail, because with light rail the city has to build the stations, buy the trains and pay the operating costs too. In economics language, the costs of public transit are internalized. The costs of cars are externalized. To figure out the true costs of roads, we must internalize the costs of cars, so let’s do that here!

The highest capacity of a lane mile is 2,000 cars per hour, but without gridlock traffic it’s 1800 cars per hour, or one car every two seconds. A road with no cars is a waste of money, and generally speaking, the more cars on a road up until the point of gridlock, the better. So let’s say 1800 cars travel per hour each direction (3600 cars total both directions) from 6am to 8pm. The average new car cost as of last year in the U.S is $33,000. Each hour we have $119 million of cars traveling. Over 14 hours in a day we have $1.7 billion of cars. But to be fair, even though this will be off too, say the people going north in the first eight hours go south the last eight hours, and vice versa, so we cut the total number of cars in half. So that brings us down to $850 million of cars in a given day traveling on that two lane road. So our total costs for that road are up to $1.05 billion. Still cheaper than light rail. But wait!

The average lifespan of a new car is eight years. That means in the 30 year lifespan of a light rail line, everyone would have to buy four cars. So that becomes $3.4 billion on cars. We have to include the car insurance costs though, which the average per car annually in the U.S is $815. At 25,200 cars both directions every day, we get $20.5 million per year on car insurance, or $616 million over 30 years. The average USian spends $2,000 annually on gas though, so we must factor in that too. The cost for buying all that gas comes out to $50.4 million per year, or $1.5 billion over 30 years.

If you add up all the costs spent on building the two lane road, buying the cars, paying the car insurance and buying the gas, the 30 year costs for a two lane road is $5.5 billion. In other words, a ten mile two lane road for cars at its most efficient use, is slightly more than twice as costly as building a light rail over the same stretch. Not to mention, the average number of people traveling per car in the U.S is 1.5. So 1800 cars per hour each direction is 2700 people being moved by car. Even if every car had five people, that’d be 9,000 people being moved each direction every hour by car for $5.5 billion. The capacity of light rail at 90 second headway, meaning its most expensive b/c of more trainsets being bought? 32,000 people each direction per hour. A light rail vehicle is 200 people, a four vehicle trainset like Sound Transit is 800 people. 90 second headway is 40 trains per hour. So yea.

A ten mile light rail line at its most efficient moves 32,000 people every hour each direction for $2.6 billion over 30 years. A ten mile two lane road at its most efficient moves 9,000 people every hour each direction for $5.5 billion over 30 years. If you get where I’m going, long story short, light rail is cheaper than even a two lane road for cars once you internalize the main costs of cars. This doesn’t include the other externalities of cars, such as increased health care costs/deaths due to pollution and/or car accidents, or the societal costs due to how much urban/commons space that roads take up.

So yea, light rail is actually more economical than a two lane road for cars when you internalize all the societal costs of cars.

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