The primary purpose of the city is transportation. Sure, we share infrastructure like sewers and power lines, but the real reason we live in dense cities is so we can have a short travel time to the things in our lives, be they jobs, friends, shopping or anything else.

Sometimes that trip is a walking one, and indeed only the dense city allows walking trips to be short and also interesting. The rest of the trips involve some technology, from the bicycle to the car to the train. All that is about to change.

Transportation has been the driver of the way we live in cities for centuries. The car was the big re-architect of cities in the 20th century, and the tram/train was the factor in the 19th. We don't always like what happened but there is no denying what caused it.

Every aspect of urban transportation is in for big changes in the next couple of decades. Even walking and cycling, to some degree.

The following are the big factors which will affect urban living choices, densities and more. I have written more about most of these topics in other locations, but let's summarize some of the big effects.

1. E-Commerce and local automated delivery -- affecting retail and value of locations.
2. Robocars -- changing the meaning of distance and location, and freeing up parking. Also rewriting the meaning of public transit.
3. Walking -- new thinking on walking (and biking) and how to integrate them with the new transportation.
4. Traffic management -- smart city techniques to remove traffic congestion and make travel times fast and reliable.
5. Telepresence -- allowing digital communication to substitute for transport.
6. Flying cars -- VTOL automated planes (where allowed) providing super fast trips and more capacity
7. Low cost tunnels -- to add new capacity, all with traffic control
8. Hyperloop or other fast transport -- connecting distant centers of polycentric cities as though they are close.

I've ordered these from the highly likely to the far more speculative. Some may not even happen, but they are getting more and more likely. Let's look at some of the factors.

E-Commerce

E-Commerce is old news, and is already greatly affecting retail. Retail of commodity dry goods is a dicey proposition now, thanks to stores like Amazon and all the delivery services. Food delivery is another hot area.

This is just the start. Also on the horizon are delivery robots, including those on the Sidewalk like the ones I work on at Starship Technologies and delivery drones, should they be allowed.

This portends the end of retail simply as local warehousing. Few will make shopping trips to buy commodity or manufactured products. Retailing will need to focus on pleasant shopping experiences, and on items that must be seen or tried on before purchase, plus items of truly immediate demand (like a snack.) Many still like to pick their produce and meats.

Food retailing also changes. Restaurants almost all already focus on dining experience. They will compete with lower cost delivery restaurants which focus only on food quality and price. Many delivery/catering "restaurants" may operate out of homes or nondescript warehouse space. Ingredients will also be delivered on a just-in-time basis to food preparers and home kitchens.

New Walkability

In a city of so many delivery and transportation options, walking becomes a choice. People will walk because they want to walk, or because the trip is fairly short and walking remains the best option because of its simplicity.

This means cities will focus on making walking desirable. Jeff Speck, who studies walkability, argues that you need walks that are productive -- you have a reason for the walk-- as well as safe, comfortable and interesting. The new options will make it harder for the walk to be the best choice for getting you somewhere, but there are many other reasons to walk like exercise, fresh air, encounters with people and lots more. The decline in the value of walking purely for transportation may require improvements in how pleasant the walk is. Speck wisely advocates against long blocks filled with large buildings which offer nothing at ground level. Parking lots, office buildings and even apartments should offer outward facing retail along the sidewalk to make them more suitable for walking past.

We'll want more pleasant and interesting spaces to walk, but ironically, we may end up riding to them. We may find people using things like my proposed neighbourhood elevator to travel to interesting walking streets for shopping, dining or walks in the park. While it would be nice for every home to be in a highly walkable area, this is unlikely to happen.

You might ask, does this describe the (dying) concept of the shopping mall? Malls are dying because old-school retailing is dying, but the idea of central spaces for walking and socializing might not fade with them.

Robocars

The massive affect of robocars is the entire subject of this web site. I have some articles on the subject (with some need of updating) such as this one on issues in urban planning and one on robocar oriented development. Here's a summary of some of the big issues:

• Since you can work, relax or socialize during travel, travel time is now productive time. This is the "death of distance" and changes the very meaning of location. I call it the poor man's teleporter.
• Public transit undergoes a massive change which includes its elimination outside of peak hours. "Stations" cease to exist.
• Transportation also becomes much cheaper with electric, single-person vehicles operating for under 30 cents/mile
• Certain synergies of "downtowns" vanish, leading to more polycentric urban spaces.
• Pollution and noise from transportation is reduced, thanks to electric vehicles.
• Some people elect to live far away and sleep and work on commutes. Others seek a denser, instant travel urban space.
• Children above a certain age gain the mobility of adults. Schools, sporting events and other activities for this age group can be in different locations
• The majority of parking lots empty out or are converted to other uses. This is a large fraction of the land in many areas. What's left becomes very cheap.
• The disabled and aged gain vastly greater mobility at a lower cost. Seniors can "age in place" in their existing homes rather than go to senior homes.

Traffic management

Robocars have potential large effects on traffic, but since there are plenty of regular cars on the road, big reductions in congestion need to come from other sources, such as congestion charging, managed lanes and more speculative plans for smartphone based traffic management.

A city with minimal traffic congestion can offer not just faster travel but reliable travel times. The quest for reliable travel times is what drives the very expensive and wasteful practice of making private right-of-way for transit lines. A 4 square mile area where you can get anywhere in 5 minutes would have high appeal.

Telepresence

Telepresence is already here, but we don't find it a great substitute for direct physical presence yet. Nonetheless, more and more people are working from remote locations some of the time, just not all of it. As telepresence technology improves, graduating to full human eye resolution, virtual reality and robot embodiment, expect this to increase. We still like to be together in person, so this hardly means the complete dissolution of the city, but it will reduce the transportation load and made certain locations more favourable for life and work.

Flying Cars

Flying cars -- or more probably VTOL multirotor helicopters -- have had their major engineering problems solved. New electric designs can be efficient, and a lot quieter than regular aircraft, though not as silent as you would like to have them take off from your neighbour's yard.

We should see such vehicles that can take off and land from building rooftops, industrial areas, transit hubs and in particular, almost anywhere along a waterfront for travel to anywhere else along that waterfront. We may see much more. At first, these will be tools of the rich, but the electricity cost of such flight I now estimate will be just 5 cents/mile -- it is the vehicle and operations which will drive the cost.

Flight offers totally new capacity, not needing the roads, and of course, direct "as the crow flies" travel. It also offers access to hills that surround cities that are hard to access, and small islands around harbour towns. Even if the flying vehicles can't land everywhere, there will be robocars waiting where they can land for quick transfer. In towns with large waterfronts such property might become even more valuable due to the flight potential.

At current noise levels, it is anticipated there will be complaint if vehicles take off within about 500 feet of quiet residential areas. Residential towers are a different story, particularly if they are built with this in mind.

Low cost tunnels

While still a research project, Elon Musk's The Boring Company offers a tantalizing promise. They theorize that by combining very small tunnels with improved tunneling technique, they can reduce the cost of tunnels by much more than a factor of 10. This is not so impossible, since much of the cost of the tunnel goes up with the square of its diameter. Typical train and car tunnels might be 24 feet in diameter while a single lane tunnel for a small car pod might be just 6 feet.

Low cost tunnels would be used by robocars, descending to them via ramps or elevators, eliminating the immense cost of stations. Tunnels can go almost anywhere, travel in straight lines and you can have an arbitrary number of levels, with no need for intersections when they cross. They don't disrupt the surface at all. With traffic management they will offer fast, reliable travel times for smaller vehicles.

Elevated tracks

Networks of lightweight robocars (for 1-2 people only or cargo) can also travel on lightweight elevated paths dedicated only to them. Such paths are much less expensive to build than full elevated roads or tracks, and they are less obtrusive, though they clearly do create some visual blight. If tunnels are not practical, we already know these are.

Hyperloop

It's still closer to science fiction, but several teams hope to attain evacuated tube transportation. While this has been dreamed of for many decades, today real efforts are going forward. The advantages are huge -- arbitrarily fast transport with minimal energy usage -- but there are still big engineering problems to solve.

Transport at 700mph or more means connecting different cities almost as though they are one city from a travel perspective. Particularly if one transfers quickly from the tube travel to robocars to continue a journey door to door.

Consider San Francisco to Oakland in under 2 minutes (at 1/2g) or Dubai to Abu Dhabi in ten minutes. For those within a short distance of the stations, it would be as though they were in both cities at once. In addition, dense cities could connect themselves to empty "green field" locations via 5 minute trips -- it would be as though suddenly several square miles of developable land appeared within the city. Anywhere with a hyperloop-style link to the CBD could be viewed as effectively being in the CBD with all its synergies.

(I will note that Hyperloop through a faultline presents much larger challenges, which is bad news for the west coast.)

The city of the future

All of this adds up to a city of the future that's hard to predict. Some of it points at more sprawl, some at more density. Some visions have the death of retail, others bring it forward in a new way.

This also combines with changes in the nature of exurbs and rural locations. The combination of online shopping, remote work and the flying car suddenly make all sorts of distant (or hard to access) locations quite viable.

Most urban dwellers would like it all -- a large lot and a big house with a view and no maintenance, with good schools and an interesting safe, walkable neighbouhood with nice neighbours. Normally tradeoffs are made. Some of those tradeoffs will change due to new transportation.

My current predictions are quite uncertain, but I suspect we'll see:

• More polycentrism: A less "downtown" oriented city with more clusters of density and retailing
• Some exodus to the exurbs, for those who truly crave lots of land or country experiences, or in some cases, lower cost.
• New dense neighbourhoods with more level pricing, since no unit has a particular advantage of being close to the transit or restaurants.
• More open malls, outdoors (weather permitting) but curated, designed for robocars to bring people in and out easily.
• Infill of parking lots with condos, or new public spaces.
• More price appreciation in the areas most desired for living, due to easier commutes from them.

What are yours?