Transportation

Sharing Isn't Caring In Transport: We Use The Word Two Ways, And Don't Understand Either


For some, “sharing” means riding in a vehicle together.

Brad Templeton

One of the more confusing words frequently associated with robocars (and all discussion of the future of transportation) is “shared.” Unfortunately, this means two very different things, with quite different consequences.

Sometimes it refers to serial sharing, namely that one vehicle goes out and serves many customers, rather than being a privately owned vehicle. There was a perfectly good word for that in the past — taxi — but companies like Lyft and Uber, when they first started offering such services, had legal reasons to try to pretend not to be taxis, so they called it “ride share,” pretending that somehow the driver of the car was just sharing a ride with the customer. They even called the payment an “optional donation” to begin. Today, you still see places calling Uber and Lyft “ride share,” though some like terms like “taxi network company” or “ride hail” or “app hail.”

It is also used to refer to multiple people riding in the same vehicle, be it traditional carpooling, UberPool style true ride-sharing, or plain old transit services.

Taxi “sharing”

We’ve all seen what app summoned taxi services have done to transportation. It’s giant, but what’s giant is not the “sharing” part. Yes, several people use a vehicle that is normally was used and owned by one person and sat idle most of the day. But that doesn’t do anything to reduce traffic congestion, and in fact makes it slightly worse. It also doesn’t inherently do anything to the number of cars made. While privately owned cars do sit unused most of the day, the waste in that is smaller than people think.

Some use “sharing” to mean a taxi, an Uber or even a rental car

Brad Templeton

In the taxi world, cars all wear out by the mile, not the year. In the private ownership world they wear out by both miles and years, an, in fact, are designed to wear out evenly between the two. Once cars wear out by the mile, it doesn’t matter at all how many people share them. If a car lasts 200,000 miles, it’s almost the same if one person uses it 10,000 miles a year for 20 years, or 5 people use it 50,000 miles for 4 years. It saves a small amount of capital. The number of cars you must make is equal to the number of miles cars travel divided by the number of miles a car lasts, no matter how many people share.

It does save parking. If you have a fleet one fifth the size, it needs less than 1/5th the parking. (Less because the cars are on the road more, not parking at all.) That’s good news, and means we get to reclaim a lot of land in cities, as well as garages and driveways. But again, that’s not what people usually imagine as the big benefit of “sharing.”

You can reduce the number of cars made if you make cars last more miles. That is easier to do with taxis than private cars because private cars already can last as many years as most people want.

Ride pooling

The more interesting type of sharing — we would call it “ride share” if that term had not been repurposed — might better be called ride pooling. Riding together actually had a much larger effect on how many cars are made, because it reduces vehicle miles traveled, and again, the number of cars made is the VMT divided by the lifetime of the car in miles. Pooling means you get the same passenger miles traveled for fewer VMT.

Pooling also offers the ability to reduce congestion and increase the passenger capacity of our infrastructure. It can also be cheaper and use less energy per passenger, if done right. This is, of course, the common rationale behind transit.

On the surface, the win is obvious. A look at any modern road shows vast amounts of unused seat capacity driving by. If all those 5 passenger cars with 1-2 people in them filled up, the capacity and efficiency of the roads would be enormous.

Unfortunately, “If done right” turns out to be crucial. U.S. transit systems tend to cost more per passenger mile and amazingly, according to the Dept. of Energy, use more energy per passenger mile on average than private cars, especially efficient or electric private cars. I have touched on these issues before.

If it is done right, with mostly full “rightsized” vehicles for group travel and the use of small and light one-person vehicles and scooters for solo voyagers, the benefits of ride pooling can be great. So great that we probably don’t need any new road infrastructure to handle all our current travel load and much more, allowing us to spend infrastructure budget on maintenance and minor tweaks instead of big projects. Consider that a theoretical single highway lane filled with nearly full 15 passenger vans following on a robot’s one-second headway could carry over 50,000 people per hour — more than any one subway line, and more than 15 lanes of regular use freeway. In practice, it would not be that good but it has the ability to get much closer because rider compromise is minimal.

Unless we can get Uber and Lyft and the rest to stop calling their services “rideshare,” it seems that the use of the word sharing is doomed to be ambiguous and confusing. Those I propose we just use terms like “taxi,” “ride-hail” or TNC for one, and pooling or ride pooling (and carpooling) for the other.

And then get down to making the benefits appear as the robocar technologies percolate into society in the 2020s.



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