If you don’t follow the work of MIT’s Senseable City Lab, I highly recommend that you start. 

Earlier this year, researchers from the Massachusetts Institute of Technology, the Swiss Institute of Technology, and the Italian National Research Council developed something that they call “slot-based intersections.” In a world where cars have sensors and drive themselves, it is intended as a more efficient alternative to traditional intersections. Goodbye traffic lights.

Much like air-traffic control, the way the system works is by assigning individualized time slots to each car for when they may enter an intersection. For example, in the diagram below (Sequence 01) the car approaching from the bottom left (#10) has a “stop distance slot” in front of it reserved for 3 of the cars that are currently in the intersection. The two that are traveling perpendicular to it and the car currently turning left into the same lane as #10 (on the other side of the intersection). The car in the midst of turning right (#5) is exempt because there’s no possibility of collision. 

In Sequence 02 (below) you can see that car #10 is now turning left, which means it has its own time slot in the intersection. Other approaching cars now have a “stop distance slot” dependent on car #10.

In all cases, cars making a right turn are able to move freely, provided they will not interfere with any other cars.

The researchers estimate that real-time slot allocation might double the number of vehicles that a traditional traffic-light intersection can handle today and, in some cases, it might completely eliminate stop and go traffic.

Often when I write about self-driving vehicles I hear people tell me that cars are still cars. It doesn’t matter whether they are self-driving or not. The same inefficiencies apply. They are not the solution to urban gridlock. Elon Musk was also criticized (following his Master Plan) for not properly understanding urban geography.

But self-driving cars will create new efficiencies. I am not saying that they are a silver bullet, but I am saying that they will help a great deal. I don’t think that anyone truly understands the extent of these efficiencies, but there are a myriad of possibilities. This Senseable City Lab project is a perfect example.

What I am grappling with right now is the relationship between self-driving vehicles and traditional forms of public transit. Until we get a handle on the efficiencies and overall impact, it’s hard to ascertain how these different forms of mobility will work together. My gut tells me that the lines are bound to get blurry and that self-driving “cars” will feel less and less like the cars we know today.

Below is a video that was published along with the research. If you can’t see it, click here.

[youtube https://www.youtube.com/watch?v=4CZc3erc_l4?rel=0&w=560&h=315]

Jarrett Walker of Human Transit recently published an interesting post talking about downtowns. His argument is that we shouldn’t be planning our transit networks around the traditional notion of a single-centered city.

Here’s a snippet:

So growing a single downtown isn’t the key to becoming a great transit city. Quite the opposite, it’s best to have a pattern of many centers, all generating high demand, and supporting balanced two-way flows between them that let us move more people on less infrastructure.  This is the great advantage of Paris or Los Angeles or the Dutch Randstad over Chicago or Manhattan.

Now, there are many cases where a singular economic center still dominates an urban region. See downtown Toronto. And many will argue that the current economic environment is creating more, rather than less, concentrated urban spikiness.

But at the same time it is quite clear that many of our cities have shifted away from a monocentric model to a polycentric one. 

I mean, just look at all employment nodes that have developed across the Toronto region. The idea that everyone comes downtown in the morning and then leaves in the evening has become an anachronism for many. Early in my career I spent 4 years commuting from downtown to the suburbs.

So what is happening is that our cities need to start performing more like point-to-point networks. This isn’t a new thought. But it’s a lot harder to execute on compared to what many cities have been used to. 

You need a critical density of both residents and employers and the right kind of connectivity to create a true “mobility hub.” In Toronto, you could argue that we really only have one of those and it’s centered around Union Station.

But I think that will change for many cities. And when we do get it right, we will be doing a lot to improve the crippling traffic congestion that so many of our cities are suffering from.

If you don’t follow the work of MIT’s Senseable City Lab, I highly recommend that you start. 

Earlier this year, researchers from the Massachusetts Institute of Technology, the Swiss Institute of Technology, and the Italian National Research Council developed something that they call “slot-based intersections.” In a world where cars have sensors and drive themselves, it is intended as a more efficient alternative to traditional intersections. Goodbye traffic lights.

Much like air-traffic control, the way the system works is by assigning individualized time slots to each car for when they may enter an intersection. For example, in the diagram below (Sequence 01) the car approaching from the bottom left (#10) has a “stop distance slot” in front of it reserved for 3 of the cars that are currently in the intersection. The two that are traveling perpendicular to it and the car currently turning left into the same lane as #10 (on the other side of the intersection). The car in the midst of turning right (#5) is exempt because there’s no possibility of collision. 

In Sequence 02 (below) you can see that car #10 is now turning left, which means it has its own time slot in the intersection. Other approaching cars now have a “stop distance slot” dependent on car #10.

In all cases, cars making a right turn are able to move freely, provided they will not interfere with any other cars.

The researchers estimate that real-time slot allocation might double the number of vehicles that a traditional traffic-light intersection can handle today and, in some cases, it might completely eliminate stop and go traffic.

Often when I write about self-driving vehicles I hear people tell me that cars are still cars. It doesn’t matter whether they are self-driving or not. The same inefficiencies apply. They are not the solution to urban gridlock. Elon Musk was also criticized (following his Master Plan) for not properly understanding urban geography.

But self-driving cars will create new efficiencies. I am not saying that they are a silver bullet, but I am saying that they will help a great deal. I don’t think that anyone truly understands the extent of these efficiencies, but there are a myriad of possibilities. This Senseable City Lab project is a perfect example.

What I am grappling with right now is the relationship between self-driving vehicles and traditional forms of public transit. Until we get a handle on the efficiencies and overall impact, it’s hard to ascertain how these different forms of mobility will work together. My gut tells me that the lines are bound to get blurry and that self-driving “cars” will feel less and less like the cars we know today.

Below is a video that was published along with the research. If you can’t see it, click here.

[youtube https://www.youtube.com/watch?v=4CZc3erc_l4?rel=0&w=560&h=315]

Jarrett Walker of Human Transit recently published an interesting post talking about downtowns. His argument is that we shouldn’t be planning our transit networks around the traditional notion of a single-centered city.

Here’s a snippet:

So growing a single downtown isn’t the key to becoming a great transit city. Quite the opposite, it’s best to have a pattern of many centers, all generating high demand, and supporting balanced two-way flows between them that let us move more people on less infrastructure.  This is the great advantage of Paris or Los Angeles or the Dutch Randstad over Chicago or Manhattan.

Now, there are many cases where a singular economic center still dominates an urban region. See downtown Toronto. And many will argue that the current economic environment is creating more, rather than less, concentrated urban spikiness.

But at the same time it is quite clear that many of our cities have shifted away from a monocentric model to a polycentric one. 

I mean, just look at all employment nodes that have developed across the Toronto region. The idea that everyone comes downtown in the morning and then leaves in the evening has become an anachronism for many. Early in my career I spent 4 years commuting from downtown to the suburbs.

So what is happening is that our cities need to start performing more like point-to-point networks. This isn’t a new thought. But it’s a lot harder to execute on compared to what many cities have been used to. 

You need a critical density of both residents and employers and the right kind of connectivity to create a true “mobility hub.” In Toronto, you could argue that we really only have one of those and it’s centered around Union Station.

But I think that will change for many cities. And when we do get it right, we will be doing a lot to improve the crippling traffic congestion that so many of our cities are suffering from.