I was asked by the New York Times to comment on what future city transportation plans should look like. In a short piece, they could not repeat all I said, so I will expand a bit here.

My main advice to cities is that nobody, including myself, has the exact answer on how transportation will look in 2030 or beyond. (They are making plans for 2030 and even 2040 now.) Because we can't know, my advice is to design to be flexible. Design to be able to change your mind.

To do this, I call upon the internet's "stupid network" principle that changed the world. Simple infrastructure, and intelligence at the edges. This means stupid roads and smart cars. The roads should not dictate the solution as much as it can be avoided. Bare pavement carries pedestrians, bikes, motorcycles, scooters, vans, cars, robots, trucks, buses and vehicles yet to be invented, while rails carry only trains, trains or trains. If building rail, consider having rail embedded in pavement -- or someday even paving over the rail because of how expensive embedded rail is.

My personal feeling is we don't need new infrastructure. Incredible capacity gains in the roads are possible. Look at any road and count the empty seats going by, and then the empty slots, even at rush hour. Replace each car with a 16 seat robotic van and consider the capacity. It's immense -- in theory.

Not everybody believes that, and they see new infrastructure as the only choice. I understand why they might be skeptical of grand visions.

BRT

As an alternative, I suggest they consider new variants of Bus Rapid Transit. BRT is already popular in many places around the world, and growing in the USA. It is effective, but vastly cheaper than the darling of transit planners, Light Capacity Rail. For some reason transitophiles like BRT but they love Light Rail, in spite of its high cost, atrocious energy efficiency and light capacity.

BRT can mean a lot of things. In some vision it involves taking out large numbers of regular lanes, but this is not always necessary. There are simpler visions which focus on a few special features such as:

• Synchronization to traffic lights to assure green lights
• Mixture of dedicated right-of-way and mixed lanes, regular and with priority
• Larger "stop" areas and multiple door entry/exit for high boarding throughput
• Elimination of ticket purchase or fare-gating on the bus and other causes of boarding delay
• Offline stops -- the bus does not block the road lane when it is stopped (unlike a train.)

My main reason to suggest BRT is that you aren't going to go very wrong by doing it. Whatever shows up in the future can probably make use of whatever infrastructure you build for BRT, whether it's lanes or tunnels or offline stops. It can probably make use of it even while the BRT is still running, so transition can be gradual. That's much harder for subway, LRT or other forms.

In addition, because BRT is low cost, a city won't waste that much money on wrong decisions that are obsoleted by new technology.

Hybrid BRT lanes

One useful option for BRT, as well as at-grade LRT, is to create hybrid lanes which allow use by well behaved private cars. Many cities already allow taxis into dedicated bus lanes so this is not that radical an idea. Robocars can make a promise of good behaviour which could justify their entry into such lanes, but even regular human drivers with something as simple as a smartphone might be allowed in.

In particular, I propose allowing other vehicles into the lane behind the bus. When a bus goes by, let them use the extra capacity behind it. Either for free, or paying a toll (like "HOT" lanes on the highway.) They must not, however, get in front of a bus. In fact, if a bus ever needs to hit the brakes because a car is in front of it, the camera on the bus would take a picture and that licence plate would get a fat ticket.

Of course, full carpools (including those from UberPool) might be highly encouraged to be users of these lanes, along with vanpools and other efficient road users.

To keep people from getting in front of a bus, a smartphone app could know the locations of the buses, and warn drivers to get out of the lane or pull over into spots where the bus can pass them. If a driver is approaching a bus stop where the bus is just about to pull out, they would be warned, and know to slow or pull over so the bus can pull out, and then they can safely follow that bus.

When I first described this this 14 years ago in the 7th ever posting on this blog I worried about the risk of congestion when drivers in a panic try to get out of a lane when a bus approaches. Today the smartphone can give plenty of warning, and robocars can be even better behaved.

Offline stations allow tremendous capacity, another benefit of the smartphone era. If passengers have indicated what station they want, you can generate buses which only stop where they need to and start having a bus every couple of seconds if you need it. Of course, if you do that, there would not be any room for the cars, but so that's because the road is already efficient. 40 person buses going by at 2,000 per hour produces 80,000 people/hour capacity in one lane -- more than any train line, and it's all seated express capacity, too. Off course you need much more offline stop capacity in this case, but it's doable. This is what will also eventually happen with a repurposed BRT corridor lane in the future robotaxi era.