An important belated update from the world of ridesharing – Uber is now testing a feature they are calling "Suggested Pickup Points", which directs customers to walk to nearby locations that are easier for their drivers to reach, saving time for both the driver and (in the case of UberPool) for other passengers on board. Lyft takes this even further, offering discounted rides on its Lyft Line service for people who come to meet it.

You may be familiar with an identical concept in the public transit industry, called a "stop" or "station" — a location near to destinations, but maybe not at their front door, that is cost-effective for a transit vehicle to reach. This saves the driver the time it takes to drive to the precise preferred location of each passenger, which is especially crucial if there are other passengers on board whose travel time is also valuable. (It also encourages a bit of walking where that's easy to do, which is good for you!)

This new feature illustrates how a demand-responsive service like UberPool can evolve to resemble the very fixed route bus that it often pretends to be supplanting, particularly when serving high-volume markets. Discounts for walking to a pickup point make perfect sense, for the same reason that fixed route transit should be even cheaper; the customer is taking on inconvenience in return for a more efficient transit service.

These moves show these companies recognizing the geometric logic of rigid, fixed transit: that when you connect places where many people want to go together, along a fast, direct path, the resulting service is both efficient to provide and useful to vast numbers of people.

Flexible transit sounds like it's more responsive to our needs as customers, but if you want it to be affordable it has to be efficient. The vehicle that comes to your door is intrinsically a low-efficiency concept when efficiency means "passengers/driver hour", as it will so long as the cost of service is mostly labor cost.

That's why, for decades, transit agencies have sometimes deployed flexible services in low-demand but growing markets but then replaced them with fixed routes as demand grew beyond what the low capacity of flexible services could handle. Transit agencies also know about "fixed stop Dial-a-Ride", which is the specific phase of this inevitable evolution that Uber and Lyft are exploring now.

The cool kids at Uber and Lyft are showing that for all their pretense of having invented something new, they live in the same geometric and economic space as their ancestors, and will evolve the same solutions that worked in the past. Data is cool, and technology is cool, and enraptured high-paying customers are very cool, but none of that changes the facts of space, biology and economics, ever.

Will driverless cars change all this? Not if we also have driverless buses. In that case, the math and geometry, and the nature of efficiency, will be largely the same.