Current State of Cities
The future could be reshaped by cars which are fully connected and controlled. Experts already anticipate a saturation of fully-connected, partly autonomous cars which could set the stage for downtowns to restrict traffic to vehicles with connected features in the next twenty years. Instead of traffic lights, smart infrastructure devices could guide cars seamlessly through street intersections, prioritized and designed long in advance, structured into efficient flow patterns, and yielding to the needs of pedestrians.
Some city planners are already trying to grapple with the coming of age of connected traffic. In the past two years, city planning organizations like NACTO and the NLC have responded to these developments with documents which outline possible pedestrian-oriented approaches for connected traffic.
Cities are choosing between two vastly different visions of the future. One for pedestrians, one for vehicles. Even the most primitive connected traffic technologies could empower cities like Atlanta, Los Angeles, and Shenzen to be able to process three times as many commuting vehicles into their central business districts as they do now. My Mass Transit Model re-designs Atlanta for the autonomous age. My model merges Atlanta's core business districts----not just aesthetically, but functionally----and expands Atlanta's central business district southward. My model forgoes a significant increase in local vehicular traffic and asks for some parking structures to be replaced or converted. Instead of concentrating freeway flow into existing office hubs, my model calms individual streets by using a prioritization algorithm which prioritizes freeway-oriented traffic which is spread out along Atlanta's central city freeway, which could push downtown's expansion southward and encourage conversion to autonomous mass-transit for each office district along Atlanta's central city freeway (I-75/I-85). My model combines these changes and eliminates redundancies to make way for a grid of interlocking pedestrian greenways, formed around Atlanta's topographical zenith----Peachtree Street----and the old railroads which encircle the city and are already being converted to a unified greenway called the Beltline.
Every existing city may need to determine what they believe is best for them. Atlanta, for instance, has a growing number of pedestrian-only greenways anchored on decommissioned railroads, alongside some existing railroads which could eventually become planning opportunities as freight trains are vanquished by the cost-supremacy of autonomous trucks. In parts of downtown, Atlanta's hilly geography makes it practical to build a separate higher grid of infrastructure for pedestrians-only thoroughfares above the grid of automated vehicle traffic (still with sidewalks, many with complete street features).
Designs for automated traffic need to precisely match a city's given situation, geography and desires----and it needs to be designed for more than just cars----or even mini-buses.
Stage 1: Mass Introduction of Connected Vehicles
In the next few years, cities could be able to make streets more efficient by using connected vehicles as pace cars. This could require cities to install smart infrastructure devices (5G) which coordinate connected vehicles as part of a hybrid system of both connected and unconnected vehicles. Even at this earlier stage, streets could become more effective at moving traffic. The University of Illinois College of Engineering found, even when connected cars only represent 5% of total traffic, measurable efficiency improvements can be observed because the connected vehicles are able to act as pace cars which smooth out “phantom traffic” where too many vehicles enter a flow at once.
As more vehicles roll out of factories with connected features, I conservatively expect connected vehicles which are autonomous enough to not only receive information about surrounding cars but be guided by the system itself to surpass 5% of all traffic in the mid-to-late-2020s.
Stage 2: Freeways Become Connected
Connected vehicles could enjoy the benefits of needing less reaction time, and thus less spacing between cars, than human drivers----especially when they do not need to evade or handle human drivers. Under the industry standard first proposed by Intel, connected vehicles could only need one second for reaction time, and they could need an extra second of reaction time where human drivers and connected cars are mixed. Even where freeways cannot be segregated into connected and unconnected traffic, connected vehicles mixed into a hybrid system could still make streets and freeways more efficient.
Business districts which cannot make accommodations could be in danger of falling behind.
Stage 3: downtowns Become Connected & controlled
Connected-only traffic systems could be able to move connected-only traffic much more effectively than a hybrid system. With all new cars including these connected features----and older vehicles aging out over time----connected vehicles could become standard. Pressure could mount for business districts to begin requiring all arriving traffic to be connected, leading to the next stage of the autonomous city.
City planners are already being asked to make decisions now without being able to design for how traffic could move at this stage. In response, Autonomous Symmetry has already made basic mockups of every major American city and some European and Asian cities—in addition to spending five thousand hours building demos for Atlanta’s streets precisely for when Atlanta's business districts enter this stage. This kind of automated traffic analysis can inform decisions like building permits, infill projects, and new infrastructure, long in advance.
Stage 4: Freeways Become Connected & Controlled
Connected vehicles could enjoy the benefits of needing less reaction time, and thus less spacing between cars, than human drivers----especially when they do not need to evade or handle human drivers. Under the industry standard first proposed by Intel, connected vehicles could only need one second for reaction time, but they could need an extra second of reaction time where human drivers and connected cars are mixed.
Connected-only freeways could benefit from even bigger efficiency gains by preventing too much traffic from entering at a single point----or too many vehicles entering multiple points which could arrive at a freeway exit, for instance, at the same point and moment----allowing freeways to reliably move at top speeds. This can be accomplished with selective congestion, for example, before entering a freeway entrance ramp----and in the long-run, with more effective measures, like variable pricing for peak traffic. In the future, this could be combined with autonomous mass transit to transform freeways into moving more people than a subway system can----Autonomous Symmetry has found no platform more effective, efficient, and convenient than matrices of one-way freeway-based mini-bus routes.
The early and most primitive connected traffic systems are widely expected to use freeway lanes more than twice as efficiently as freeway lanes used by human drivers. With a prioritization algorithm, traffic can be re-directed so that the only traffic allowed on a typical central city freeway is traffic which is either arriving or departing in the central business district. A 2016 GDOT traffic study showed nearly a third of Atlanta's downtown connector freeway was thru-traffic, which passes through the central business district rather than arriving or departing in it. By redirecting this traffic and changing the underlying system, connected traffic systems built around a prioritization algorithm could allow most central city freeways, like Atlanta's downtown connector, to carry three times as much traffic into their downtowns as what they currently carry.
Prioritization algorithms could also be able to prioritize specific vehicles, like emergency vehicles, but also mini-buses and other possibilities for freeway-based autonomous mass transit. Cities without detailed plans for unique prioritization algorithms long in advance could find themselves racing to catch up under increasing pressure to quickly draw plans which could increase the number of workers who can arrive in their central business districts without more time to focus on the other needs and creative visions which can create a meaningful city.
Stage 5: Reaction Time for Connected Vehicles Pushed Below Whole Second
One of the greatest changes connected vehicles could bring to traffic flows is their reduction to reaction time. While humans generally rely on two seconds of reaction time, connected-only traffic could require just one second. But what happens if technology improves and, over time, the standard reaction time drops?
Achieving just a nine-tenths of a second reaction time could drastically increase traffic flow. Freeways could benefit more than other vehicle routes. Cities without long-ranging plans may not have designed flexible systems capable of handling these changes. This is why Autonomous Symmetry has designed Atlanta’s infrastructure for autonomous car reaction times all the way down to below half-a-second.
Based on history, I do not expect most cities to adequately plan for connected traffic. Most cities are likely to be caught off-guard every step of the way. For the cities which do not prepare, their central business districts could grow more painfully, their physical forms less desirably, and their talent pools less reliably.
It can be tempting to assume new technology will make everything better for cities, so I did the math. A lot of math. I built my first simulations for Atlanta, a highly auto-centric city with a spacious downtown, tall skyscrapers, and wide streets. Autonomated traffic can produce beautiful change, but only if it is shaped, planned, and earned in advance.