Posts about Pedestrians

Diverging diamond: Faster traffic, worse for pedestrians

Diverging diamond interchanges (DDIs) are designed to move cars more efficiently by reducing the number of signal phases at interchanges and allowing cars on freeway on- and off-ramps to move freely without waiting for signals.

To accomplish this, the surface street lanes (not the freeway) cross to the opposite (left) side of the center line as they to pass through the interchange.

Pedestrians have to cross to the median and walk between concrete walls, forcing them to cross half of the through lanes at each side of the bridge. In the case of the Greenbelt Road/Kenilworth Avenue interchange, that would mean crossing 3 or 4 lanes (depending on the final configuration of the design) at each side of the bridge.

Alternatively, the design could accommodate pedestrians the outside of the roadway, but then they must cross the free-flowing left turn on- and off-ramps where drivers will be focusing on making the turn fast rather than looking for people crossing.

Incompatible with walkable vision for the corridor

What's most troubling is that the planning department is actually trying to create an urban, pedestrian environment immediately west of the interchange, yet they still proposed this design which does the opposite.

Early on in the presentation, planners showed before and after renderings of their visions for a walkable urban node where Beltway Plaza is today. They showed a suburban arterial transformed into a narrowed street with wide sidewalks, street trees, pedestrian lighting, and bike lanes. At previous meetings, they talked of building a street grid, of filling in parking lots with development, and making it easier and safer to walk in these new urban nodes.

They also talked of finding ways to link the different neighborhoods of Greenbelt that have been separated from each other by the various freeways in the area. They specifically mentioned finding better ways of linking the Golden Triangle office park with the Beltway Plaza area—two neighborhoods that are currently separated from each other by Kenilworth Avenue and its interchange with Greenbelt Road.

But planners are approaching rebuilding the Kenilworth/Greenbelt with the objective of moving more cars, faster. They are not thinking about creating a pedestrian-friendly environment in that space. They are not thinking about making cyclists feel welcome on the road.

And encouraging drivers to speed up as they approach what planners hope to be a walkable node is asking for trouble.

The cure is far worse than the disease

Today, Greenbelt Road crosses above Kenilworth Avenue at an interchange built in the 1980s. Most would agree that the intersection has its problems, mostly from the way the northbound ramps are offset and the close spacing of the north- and southbound off-ramps.

But the solution the county planners propose would be far worse than the current setup, especially for pedestrians and cyclists.

It is questionable why the county wants to focus on this intersection to begin with. It's not "failing" by traffic engineer standards, and in terms of driver delay, it's not even the worst intersection in the corridor, according to a study conducted in conjunction with the Sector Plan. But of course, highway engineers like to "fix" things whether or not they're broken.

Strong Towns executive director Chuck Marohn narrated a video about a DDI in Springfield, Missouri. A traffic engineer involved in the design created the video, touting how a pedestrian can walk through the interchange, but Marohn points out how absurd it is to say that this is actually pedestrian-friendly.

Marohn notes that while a DDI provides a path for pedestrians and cyclists, it's nothing like the kind of interchange one would design if the goal from the start were to make a space friendly to people walking and biking.

Building walkable communities and complete streets has to be more than an engineer running down an accommodation checklist. If we're trying to create a neighborhood where walkability is a primary goal, then pedestrians, cyclists, and transit users have to be a top priority, not just get the leftover road space and the bare minimum listed in the design guide.

The nascent urban districts at White Flint and Tysons Corner are transforming from suburbs to more walkable spaces. And like the Beltway Plaza area, pedestrians in those areas face barriers in the form of interchanges. Prince George's can't simply get rid of their interchanges, but they don't need to make the pedestrian condition worse by recommending converting an interchange to one that's sole purpose is to move cars more quickly.

JBG recently began demolishing several buildings on the southwest corner of 14th & U Streets, NW to prepare to build of a major, mixed-use project. The sidewalk on the west side of 14th Street abruptly closed, with a fence blocking it off for more than half the block.

The 14th Street corridor has endured near-constant construction for several years now. Other projects have included varying types of temporary walkways, from bare-bones plastic jersey barriers to lit, covered scaffolding. When construction activities have required closing the sidewalk altogether it generally been for only a day, if not hours, at a time. Why not here?

No sidewalk during raze

Eric Fidler posed the question to DDOT, and an inspector gave this response:

The sidewalk is closed and pedestrians are routed across the roadway in accordance with DDOT's Pedestrian Safety and Work Zone Standards. This policy provides a matrix for what methods of pedestrian access are the most appropriate based on the phase of construction. In this case the project is undergoing raze. During raze activities the sidewalk is to be closed with pedestrians routed across the street.

Raze is a short period, typically lasting a few weeks to just more than a month. After this phase the sidewalk is to be opened or a pedestrian walkway is to be provided. It is DDOT's goal to maintain the pedestrian path on both sides of a roadway and will only allow the closure when it is unsafe to maintain it or when the work requires that the sidewalk be closed (e.g. during sidewalk construction).

It's true that DDOT's guidelines recommend closing the sidewalk during the raze. But is that appropriate? A raze doesn't mean dynamiting the building so it just collapses. Workers spend most of the raze period carefully removing materials, mostly from the interior and rear of the block.

Meanwhile, many active sites around the city long past the raze stage pose far more potential danger to pedestrians than sites razing existing structures. A few blocks north on 14th Street, a large 11-story building is being constructed with a covered walkway along part of the frontage, and an in-street, open walkway along the rest.

Recently, tower cranes have been lifting multi-ton sections of preformed concrete into place, frequently swinging directly above the pedestrians walking below. What about that poses less danger than a one-story brick facade being knocked down on the interior of a block?

When closing a block, especially where there are open businesses on either side, a large percentage of pedestrians will still ignore the signs and walk through along the fencing. By closing the sidewalk altogether under the auspices that any pedestrian accommodations would be dangerous, it creates a far more dangerous situation. Not only do people still have to walk past the construction entrance, they're doing so in traffic.

Mid-block closures also harm remaining businesses on either side because of the reduced foot traffic from those people that do cross the street. Even where an entire block is closed, businesses on the same side of the street on adjacent blocks likely see a drop in foot traffic. Having been forced to cross, people generally continue walking on the opposite side of the street if the light permits.

While the weekdays produce a lot of foot traffic, the weekends are even busier, and would benefit most from a temporary walkway. Yet, on the past few weekends (and even occasionally during the week), cars could park in the curbside lane, which is used for receiving during the week. Pedestrians still had to walk in the street.

If this lane is only needed for construction activities some of the time, it should be a walkway the rest of the time, not parking spaces. If DDOT and JBG can get pedestrians out of traffic for even 30% of the week, that would be a major safety improvement.

Access creates complications

The situation at 14th & U is complicated because the strangely shaped parcel is difficult to access. The project is mostly mid-block, so it can't receive trucks and stage materials from a side street.

Alley residents are adamantly opposed to the construction company using the alley. There are several alley dwellings immediately behind the site. Many people in that ANC opposed the use of T Street for construction. As a result, the construction company can only receive trucks and materials from 14th Street. All the other projects along 14th are staging along a side street or in an adjacent alley.

JBG says they have been trying to work with DDOT to create an alternative pedestrian path. DDOT officials, however, insist that there is no safe option because the construction site entrance and staging area are on 14th Street.

A JBG spokesman said that DDOT will not let them open a pedestrian path because of this staging issue on 14th Street. JBG is still considering two alternatives, neither of which is ideal:

• Cut down two street trees and create a path in the treebox zone. There would still be issues since they would have to allow trucks and materials to cross the pathway. Trucks will be received in the parking lane as currently planned.
  
• Receive trucks in the parking lane, since there is nowhere else for them, and convert the bike lane to a pedestrian path.

While JBG's comments imply that DDOT opposes a walkway even during construction phases, DDOT's John Lisle denied that was the case. "A walkway will be provided after the razing period precisely because there is so much construction in the area," Lisle said.

Trucks turning into an alley or side street at construction sites elsewhere on 14th Street pose just as much a danger to pedestrians as those that will enter an exit the JBG site at mid-block. But DDOT hasn't closed R or Swann Streets because of the danger to people on foot.

JBG should be able to use the parking lane or sidewalk for a temporary walkway and establish a site entrance along 14th Street. They should be required to mark it very clearly, and pedestrians and construction workers should both treat it as an intersection.

Instead of being a roadblock, DDOT needs to encourage a developer that wants to accommodate all of the road users and take responsibility for everyone's safety at their site. Preserving traffic lanes and neighbors' peace and quiet is important, but so is providing safe, reasonable accommodations for pedestrians.

In the heart of downtown, the CityCenter site has been under construction for over a year. Construction has taken over the sidewalk around more than ¾ of the site, yet only the northern section has any temporary walkway.

On any given day, pedestrians walk along the construction fencing on 9th, 11th, and H Streets, in traffic because they don't want to deal with the hassle and delay of sometimes 4 additional crosswalks to get to their destinations.

Throughout the site excavation, the developer closed all the sidewalks. This happened despite DDOT's policy stating that an open or covered walkway should be provided on the sidewalk if possible, or otherwise in the roadway. Once frame construction begins, which happened recently, the preference then is a covered walkway in the roadway.

At the construction site of the Convention Center hotel a few blocks north, at 9th and Massachusetts NW, the sidewalks there have also been closed for months throughout multiple stages of construction.

The problem is not unique to Northwest. In Northeast, on Bladensburg Road near the "starburst" intersection, the sidewalk is closed for an entire block on the north side, where a new condo development is rising. In Southeast, in the Navy Yard area, sidewalks are closed at 4th Street by the upcoming Boilermaker Shops, and on various blocks around the last phase of EYA's Capitol Quarter townhome development.

In some cases, upon receiving complaints, DDOT has inspected sites like these and then ordered the developer to provide a walkway. This is good, but pedestrian accommodation should not be reactionary. It needs to be a priority in the traffic management and permitting process.

Where sidewalk space is tight, DDOT should show leadership and use road space to create temporary walkways. Pedestrians should not have to bear the sole inconvenience of the construction. Sometimes it means closing a lane of traffic to move the sidewalk (and bike lane where necessary) out from their original location.

Stronger policies and enforcement will encourage developers to use their available space to its maximum extent, instead of leaving tools and junk lying around like the picture to the right. If they are forced to get permits for walkways in the roadway, this will also encourage them to bring construction activities back within the parcel envelope as quickly as possible, to the benefit of everyone.

On the northeast corner of the CityCenter site, the developer has managed to preserve close to 100 public parking spaces. In light of this, saying that the sidewalks have to be closed because of space constraints is simply insulting.

Some may say that the inconvenience people on foot face by having to cross the street is minor, and doesn't merit burdening construction planners with stricter requirements and additional safety measures, or potentially inconveniencing drivers by closing a lane of traffic. Yet we impose all kinds of other, more onerous restrictions on developers for far more capricious reasons.

Closing a sidewalk on one side of the street inconveniences pedestrians in the same way that closing a two-way street to one entire direction of traffic would drivers. If I am walking 4 blocks along one side of the street, and the sidewalk is closed for one of them, I have to cross at least two additional times, assuming there are no mid-block alleys, and the intersections are all simple 4-way intersections. This means waiting at least two additional light cycles and walking out of my way.

Many pedestrians choose not to endure the inconvenience, and instead endanger themselves and others by walking in the street rather than crossing.

Only in the rarest of cases are motorists asked to endure months-long closures like this. Why, then do DC's pedestrians have to deal with this every day?

As DC's urban population grows and development activity picks up again, it may be time to revisit the pedestrian accommodation policy. In the meantime, DDOT needs to better use the policy it has in place to keep pedestrians safe.

Where else in the city have builders been allowed to close sidewalks? Post them in the comments.

A genuinely educational campaign could feature messages like "Never cross mid-block between two traffic lights" or "Come to full stop before turning right on red." The slogan "Stop for pedestrians at marked and unmarked crosswalks" would stimulate the public's curiosity, since few know about unmarked crosswalks (places where the pavement has none of the familiar crosswalk lines, but a crosswalk still legally exists, and drivers still must yield to pedestrians crossing the street).

Highway agencies recognize that education about pedestrian safety must accompany engineering and enforcement. But our region, especially outside the District and Arlington, has a spotty record in engineering and enforcement. That makes educating the public about pedestrian safety all that more important.

People walking along 23rd clearly don't want to, and shouldn't have to, cross up to 6 roads just to traverse the circle. Instead, they cross where there is no light and then walk on the grass. Well-worn "desire lines," especially on the north and south sides to get to 23rd Street make this very clear.

The National Park Service and DDOT want to fix this. Fortunately, instead of using the strategy of just fencing off parks to stop pedestrians, as they wanted to do for the triangle park at Q Street and the Dupont Circle Metro, the Park Service is doing the right thing: they will add walkways and move some.

DDOT will add crosswalks and new signals that line up with the new walkways. After this project, every pedestrian crossing in and out of Washington Circle will have a traffic signal. DDOT also plans more signals and crosswalks on the roads between the circle and Pennsylvania Avenue or K Street, letting pedestrians cross directly in sensible directions.

The plan also calls for a fence around the remainder of the circle. This will stop people from walking in and out at other places.

I'm not very enthusiastic about this recent NPS push for adding more fences. Down the street from Washington Circle, they're proposing another fence, also to "eliminate the creation of social paths," for the triangle between 21st, I, and Pennsylvania NW.

Instead of holding the existing layout sacrosanct, at Washington Circle, they are working to accommodate pedestrians. By placing crosswalks at the main places people want to cross, this traffic circle is about to get a lot safer.

They analyzed a number of options and condensed them down to 3 bicycle and pedestrian options, 4 roadway options, and 6 Transportation Demand Management options. This post looks at the roadway and TDM alternatives; the next one will delve into the bicycle and pedestrian options.

Vehicular options

One of the most significant conclusions from the draft EIS is what it chose not to recommend: More single-passenger vehicle capacity. The team looked at adding new general-purpose lanes (which, on a freeway-type bridge, aren't as much "general purpose" as "motor vehicle only") or HOT lanes. Once Virginia decided not to run HOT lanes through Arlington, the HOT lane options became moot, and adding new auto capacity generally did not reduce congestion.

There are 5 remaining proposals that would affect motor vehicles:

Add a bus lane. A lot of commuter buses drive to the Pentagon and then over the 14th Street bridge to DC, and many local buses also cross in this area. This alternative would use the existing shoulder of the Rochambeau bridge (the center of the 3 road bridges, which carries the express lanes in both directions) for a bus lane, and convert one lane on 14th Street to a bus lane.

The heavy volume of buses moves a great many people in this corridor. Helping buses bypass congestion and give riders a quicker ride would further improve the value of taking transit from many parts of Virginia.

Ban left turns at 14th and C (at a cost of about $203,000). C Street SW ends at 14th, in the last intersection with a traffic signal before the bridge. The study says that giving time for vehicles to turn left from southbound 14th onto C, or left from C onto southbound 14th, creates significant delay, and this option would forbid these turns. Drivers would only be able to turn right in or out of C.

On its own, this sounds like a bad idea because it would move further away from a functional grid in this area, and make 14th more like a freeway. It could, however, be a reasonable way to reduce some of the extra delay that comes from the bus lane option, making that a little more palatable.

The most important question, which the report does not specify, is how this would affect pedestrians. People cross on foot to get to and from the Holocaust Museum, for instance, and already the signal here forces them to wait long periods of time for the various movements. Removing the left turns could allow more pedestrian crossing time, or it could make things worse, depending on the final signal timings.

DC should also add a marked crosswalk along the south side of this intersection, where there is none today. Every side of every intersection ought to have a marked crosswalk, regardless of its effect on traffic, but an animation of the proposal makes it appear that there would be no traffic effect with left turns prohibited, anyway.

For the final EIS, the team should investigate pedestrian crossings and suggest timings that help them cross more safely and with a shorter wait.

Restripe around Maine Avenue, 7th and 9th Streets ($185,000). There are a lot of ramps on and off in this area, creating a lot of merging and weaving. This option would narrow the on-ramp at Maine Avenue to 1 lane instead of 2, reducing the amount of merging on the freeway itself.

Also, it would add a solid white line between some of the freeway's lanes east of 9th Street. Drivers getting on at 7th Street would only be able to then continue to the 3rd Street tunnel (the one that goes under the Mall to New York Avenue, also signed as I-395), and drivers getting on from 9th Street would have to continue onto the Southeast Freeway (now signed as 695) instead. Drivers might ignore this line, but FHWA hopes it will decrease weaving.

Remove some ramps on the Virginia side ($2.7 million). There are 10 ramps on and off 395 right around the Pentagon, also creating a lot of merging and weaving. This alternative suggests removing the ramps from 395 northbound to the GW parkway northbound, and the matching ramp from the GW Parkway southbound to 395 southbound. Drivers can still get where they need to go by taking Washington Boulevard (Route 27) instead, which is actually shorter, anyway.

In addition, this alternative would change around the ramps at Boundary Channel Drive, the access road to the Pentagon north parking lots. Now, there are cloverleaf-style ramps on and off of 395 southbound, so that cars coming from or going to each direction of Boundary Channel have their own ramps.

Instead, the ramps in the southwest quadrant would go away, and the northwest quadrant ramps changed so that cars can turn in either direction on and off of Boundary Channel.

Arlington has proposed another option to add roundabouts instead of traffic signals at the ends of the ramps.

Transportation Demand Management options

Reconfiguring roadways is not the only way to reduce congestion. Transportation Demand Management is the field concerned with helping people better understand their travel options besides solo driving. Maps, real-time information, and public service ad campaigns can help people choose transit. Employers can provide incentives or assistance for people to carpool, telecommute, or commute outside peak hours.

The TDM options that the DEIS proposed to carry forward to the final version include:

• Expand incentives for telecommuting
  
• Expand flexible work hours
  
• Increase prices for parking and/or decrease supply
  
• Better coordinate among agencies along the corridor (Federal, District, state, and local) to share information and respond to crashes or other incidents
  
• Create a program to educate drivers in the corridor in "[crash] avoidance maneuvers and defensive driving skills"
  
• Make signs better and more consistent across the corridor

The study team is accepting comments on the draft EIS until March 15th. They will then begin work on the final EIS. I will send them all comments made on this post through at least the end of Wednesday, March 14. If you want to send them your own, more detailed comments, you can do so through this form.

The bicycle and pedestrian proposals, meanwhile, are worth a whole discussion on their own. Part 2 will examine these in detail.

If you want to cross a road, you'll just cross. The cars will slow down and avoid you. You could cross blindfolded and be perfectly safe. You'll be able to cross freeways. You'll be able to walk diagonally across intersections. You'll be able to do anything you want, and the cars will be responsible for avoiding you. Your biggest danger will come from cyclists and other pedestrians, not cars.

It would be fantastic if this scenario came to pass, but is it realistic? It's certainly possible computers can get smart enough to handle it, but the sticking point here is the words "will slow down."

How much will they slow down? For how many pedestrians? Drum lives in Irvine, California, which has few pedestrians, so perhaps the cars can just avoid the occasional pedestrian. But in urban areas, there are a lot of pedestrians. If everyone crossed whenever they liked, the cars would slow down an awful lot.

In some places, cars would hardly ever get through. In almost any major city's downtown during a busy period, pedestrians are waiting in large numbers on street corners to cross. The only reason cars can get through is because signals govern pedestrian crossings. And when a light is green, often a car has to wait for a gap in the pedestrians or gently nose through to get past.

In Kevin Drum's future urban cores, constantly crossing pedestrians mean that car traffic will not flow at all except perhaps in the wee hours. Anyone who's been involved in a proposal to take away a lane of a road for bikes, or for a road diet, knows that drivers (or, in the future, car riders) will not stand for it.

Drivers are a powerful political force

Just look at, for example, the backlash against a bicycle lane on Prospect Park West in Brooklyn. In a very liberal jurisdiction, a modest and overwhelmingly successful bike lane nevertheless stirred up a few wealthy and well-connected individuals, including the wife of Senator Chuck Schumer (D-NY), to create an organization and file lawsuits to block the project using any means necessary.

Tea Partiers certain that there is a vast UN conspiracy to force them to live in high rises are opposing even extremely modest state laws creating some incentives for development in dense areas. Do we really think people will let government mandate that nobody is allowed to drive a car by hand, and that pedestrians get absolute priority?

In the DC area, some bicyclists ride on MacArthur Boulevard in Potomac, a narrow and windy road in a low-density area. That's perfectly legal, but there's a constant stream of letters to local press outlets by drivers who are sure it must be illegal to bike there since it slows them down.

Forcing drivers to travel slower would be like telling seniors that we're cutting their Medicare. The political counter-pressure is intense, so much that most transportation planners always take great pains to reassure drivers of how any change won't really slow them down. Even for the pedestrian plaza in Times Square, one of the early promises from the mayor's office was that it would actually reduce car delays.

I can go on. But anyone who writes regularly about transportation has encountered the massive sense of entitlement from drivers. When I'm driving, I hate to be delayed, too, but I squelch this natural impulse because I write about the issues and have context.

It may well come to pass that driverless cars have to travel slower and pedestrians are able to act more freely. But this will create tremendous political pressure to change the social compact over roads to get traffic moving faster once again. And in this, we will see another, more intense variant of the same fight we have today.

Once, pedestrians did walk freely, and children played in the streets. As automobile use proliferated, rising deaths led to campaigns to segregate street space. Our society could have taken one of two approaches: it could have limited drivers, and added legal liability to force drivers to be more careful, or it could get people out of the street. Many places in Europe chose some elements of the former, but America decisively chose the latter: to redefine the street's role in society to move cars faster. I'm certain that in Drum's scenario, there would be intense pressure to do the same.

Who is liable?

One element determining whether driverless cars turn into the Kevin Drum reality or another one is how we treat liability. When a driverless car kills a person, whether due to a human overriding the technology or a failure in the computer system, there will be a lawsuit.

If courts hold that the manufacturer of the car is liable, this will stifle development of the cars. The technology might ultimately be perfect, but it won't be perfect from the start. Manufacturers will ask state legislatures to limit their liability. Already, a number of commentators have called for liability caps or other legal changes which shift the burden away from the manufacturer.

If the legislatures don't agree, then manufacturers will have to move very carefully until they can make the cars virtually incapable of killing anyone. That will likely hinder development in general, and make any self-driving cars travel slower than human-operated cars. Many drivers therefore will turn off computer mode a fair amount of the time, and political pressure will build to change the liability standard. This will be an early skirmish in the battle over the cars' speed.

If states do limit liability, then we'll end up with a different situation. Buyers will want driverless cars that use algorithms like the one the University of Texas team devised that let them move faster. Sometimes those cars will travel close to pedestrians or bicyclists. Most of the time they'll still avoid killing anyone, but mishaps will happen. And like in today's legal world, prosecutors, judges and juries will be very reluctant to impose heavy punishments on someone operating a car who unintentionally kills another.

Then we'll be back to a situation like the early 1900s roads. For people's own safety, officials will start imposing restrictions on pedestrians. It'll start in places like Irvine. If laws won't stop people from walking on highways or crossing diagonally, then they'll build fences, or skybridges, or both.

Today, one argument against restricting pedestrians too much is that not everyone can drive. Seniors and people with disabilities can't operate a car, and many can't afford them. When driverless cars become commonplace, there will also be cheap taxi service, and so it'll be easier just to tell people to call up a car.

Already, many suburban areas are essentially an archipelago of human-accessible islands in a sea of almost-cars-only space. Little will stand in the way of making this other space absolutely cars-only. And why not? After all, without people, cars can use fancy algorithms to interweave with each other and zoom around far faster than they could in 2012.

Driverless cars aren't bad

A number of the responses seem to be reacting to an imaginary variant of my thesis, in which I said that self-driving cars were going to be a unmitigated bad thing. There's a natural tendency to simplify all arguments into "x is great!" or "x is terrible!"

The fact is that autonomous cars are coming whether we like it or not, and like any technological advance, will bring both terrific improvements to people's lives as well as drawbacks.

Driverless cars are sure to lead to big fights. Will they shift the balance farther toward pedestrians, as Kevin Drum believes, or away? I hope the former, but the technology won't magically solve this problem. Instead, we'll have to fight it out through the democratic process, as we do most other issues affecting the public sphere.

Badger writes,

[H]uman-driven cars would have to wait for a signal that would be optimized based on what everyone else is doing. And the same would be true of pedestrians and bike riders.

That certainly sounds like all other users of the road will have to act at the convenience of the driverless cars, under constraints designed to maximize vehicle movement instead of balance the needs of various users.

My background is in computer science, too, and computer scientists love figuring out how to make complex systems perform efficiently. Driverless cars provide an opportunity to optimize the real-world traffic system, if you can get most people driving computer-controlled cars and can get all of those computers to cooperate.

But you can't optimize people so easily. Already, cities host ongoing and raucous debates over the role of cars versus people on their streets. For over 50 years, traffic engineers with the same dreams about optimizing whizzing cars have designed and redesigned intersections to move more and more vehicles.

These changes frequently pushed other users aside with longer waits for crosswalks, the need to push buttons to get a walk signal, awkward bridges over wider and wider arterials, or simply omitting bike or pedestrian facilities entirely and then blaming those users when careless drivers hit and kill them.

Some pro-automotive advocacy groups like to push the theme of a "war on cars," but bicyclists and pedestrians feel like there's been a war against them since the early 20th century. This Texas team's video just perpetuates that impression.

The video even depicts an intersection with a whopping 12 lanes for each roadway, at a time when most transportation professionals have come to believe that grids of smaller roads, not mega-arterials, are the best approach to mobility in metropolitan areas.

Driverless cars, therefore, are poised to trigger a whole new round of pressure to further redesign intersections for the throughput of vehicles above all else. It won't only happen in the cities, either. Suburban areas are often ground zero for these debates, where the majority of people drive, but a significant and often growing number are either unable to drive due to age or disabilities, or are unable to afford cars. (Driverless cars probably won't be cheaper.)

Suburbs, therefore, often develop a greater tyranny of the majority, where county and state departments of transportation optimize their roadways for car throughput and leave bus stops in awkward and narrow roadside spots, leave crosswalks out or even remove existing ones, and set the stage for rising deaths.

If autonomous cars travel much faster than today's cars and operate closer to other vehicles and obstacles, as we see in the Texas team's simulation, then they may well kill more pedestrians. Or, perhaps the computers controlling them will respond so quickly that they can avoid hitting any pedestrian, even one who steps out in front of a car.

In that case, we might see a small number of people taking advantage of that to cross through traffic, knowing the cars can't kill him. That will slow the cars down, and their drivers will start lobbying for even greater restrictions on pedestrians, like fences preventing midblock crossings.

Our metropolitan areas could then look, more and more, like zoos for humans interlaced with pathways for the dominant species, the robot car. Maybe the machines really are on the way to taking over, but instead of Skynet declaring war on humans, we'll be the ones passing laws and reshaping our communities for their convenience.

I'm not suggesting we avoid research into driverless cars. Like any technology, they can bring good or evil, depending how society handles them. Driverless cars can allow buses to become on-demand jitneys and virtually eliminate the need to own a personal car in a city, or to build huge amounts of parking under office buildings. Instead of storing cars during the day, they can just drive around and transport people like taxis.

But we do need researchers excited about driverless cars not to forget the human element. The goal of our built environment is not to move cars as fast as possible everywhere, but to create a better quality of life. The computer science researchers need to also talk to their colleagues in other disciplines, set appropriate goals that consider all users of the roads, and think about what algorithms can actually make life better.

Cross-posted at The Atlantic Cities.