Connected Vehicles without Speed Limitation Is More of the Same

By Peter Norton

Red light trails from passing back lights lead down a wide street. In the foreground, a ghost bike painted white is locked to a pole, which has a “A Cyclist Was Killed Here” sign.

For a century, traffic safety in the United States has been primarily a quest to make fast driving safe, especially for the occupants of vehicles. Automakers, tech companies, and government agencies are still striving to build safe streets and cars without asking drivers to slow down, even in cities, towns, and suburbs. So far, it hasn’t worked.

Technology can make cars safer by limiting their speed. A century ago, this was the preferred technique in the U.S.; in 1923, 42,000 Cincinnatians signed petitions calling for a citywide referendum. They wanted an ordinance that would require local motorists to equip their vehicles with mechanical speed governors that would limit their top speed to 25 mph to make the city’s streets safe for walking again. The petitioners succeeded in getting the referendum on the ballot, but they triggered a massive “Vote No” campaign among local automotive interest groups, and the initiative was defeated. Motordom perceived demands for speed governors as a threat to the future of cars in cities. They organized to redefine safety. Even in cities, they argued, fast driving can be safe.

Ostensibly on safety grounds, motordom favored laws that prioritized drivers on city streets, safety campaigns that taught pedestrians to defer to motorists, and engineering standards that accommodated fast driving. In 1934, motordom promised that “foolproof highways” — divided roads with grade-separated intersections and controlled access — would prevent 98 percent of traffic deaths. But such highways invited speed, and drivers accepted the invitation. For vehicle occupants, they were safer than city streets — but nowhere near as safe as promised. The highways also filled cities with drivers who expected to drive fast, even without the highways’ safety features. Pedestrians and cyclists had to manage streets where motor vehicles had priority and where lethal speeds were the new normal.

We still live with the legacy of motordom’s success in redefining traffic safety. With public funding, engineers are still striving to make fast driving safe for vehicle occupants, largely by restricting street access for others. Experts have taken a symptom of pedestrians’ and cyclists’ marginalization — their vulnerability to fast motor vehicles — and made it a defining attribute: in the jargon, they are “vulnerable road users” (VRUs). The term normalizes the vulnerability of people who are not in vehicles, as if their vulnerability is a fact of life rather than the effect of extraordinary efforts to normalize and prioritize fast driving everywhere. To people walking, wheeling, or riding a bike, fast drivers are menacing road users, but it has not occurred to the experts to call them MRUs, because experts — despite their purported objectivity — take the driver’s perspective. They inherited it from motordom’s successful reframing of traffic safety a century ago.

This history, and the interest group agendas that reinforce it, explain the pervasive bias in the official means of applying technology to improve the dismal traffic safety record in the U.S. At least in cities, towns, and suburbs, the single best way to improve safety for all, including MRUs and VRUs, would be to slow vehicles down. This would increase road capacity, reduce energy consumption, improve conditions for transit, and above all, make streets and roads less hazardous, both for vehicle occupants and for others. High-tech speed governors could limit vehicles to the right maximum for each street and vary the maximum in response to conditions. Europe now requires that new cars be equipped with such speed control. But in the U.S., proposals of this kind are almost unheard of.

A bicyclist is in focus on a dark street, while behind them, light is blurred into horizontal streaks.

Instead, official favor goes to tech that is intended to make fast driving safer. “Connected vehicle” (CV) systems, long in development, would wirelessly report vehicles’ location, direction of travel, and speed to other vehicles in the vicinity. Roadside sensors, mounted at intersections and elsewhere, could detect pedestrians and cyclists, reporting their location to nearby motorists. Bicycles can be equipped with devices that permit vehicles to track them directly. Smartphones carried by cyclists or pedestrians can also serve as means for vehicles to track them. Drivers would receive information and occasional alerts; for emergencies, automatic braking might also be implemented. Many experts see CV systems as the means of letting automated or autonomous vehicles (AVs) safely go faster.

CV systems are already big business. Across the U.S., there are 69 USDOT-funded pilot projects; 102 more are planned. For each pilot, numerous vehicles and intersections must be equipped.

Yet just as the safety advantages of “foolproof highways” were exaggerated, so are the safety advantages of CV systems. In both cases, pedestrians and cyclists are often omitted from the calculation. One 2010 report from the National Highway Traffic Safety Administration (NHTSA), based entirely on deduction from crash types, speculated that “Excluding drivers impaired by alcohol or drowsiness, [CV] systems deal with 81 percent of all vehicle crashes involving unimpaired drivers.” “Deal with” does not mean “prevent,” and the researchers warned that the systems would not protect pedestrians or cyclists. Though more recent NHTSA estimates of the crash prevention that CV systems can deliver are on the order of nine percent, the 80 percent figure is still cited by interest groups as grounds to implement them.

On a highway, CV systems could prevent the dangerous pileups that can occur when visibility is poor. At a stop light on a city street, they could tip a truck driver off to a cyclist in the truck’s blind spot. These are valuable applications. But the plans for CV systems that state and local governments are working on now reflect a persistent interest in fulfilling motordom’s century-old promise of making fast driving safe, even in cities. And wherever fast driving is prioritized, everything else is marginalized.

According to an official report from the Minnesota Department of Transportation, CV systems’ advantage lies in “allowing the vehicle to react to dangerous situations before a human would be capable of doing so.” At highway speeds, this is indeed an advantage. But the report, like reports in other states, calls for CV systems in urban and suburban settings. On ordinary roads and streets, speeds that are too high for human reaction times are simply too high, even for connected vehicles. CV systems may have a slight advantage in reaction time, but they cannot reduce the stopping distance once the brakes are applied. Even an ideal “V2X” (vehicle-to-everything else, such as people not in vehicles) system would need about 40 feet to stop a vehicle traveling 30 mph. Traveling at 20 mph, the vehicle could manage the stop in about 18 feet. In a collision between two cars, the consequent difference in the force of impact may matter only in terms of vehicle damage. But wherever people may be walking or riding a bike, the stakes are life and death.

A silhouette of a man crossing a Manhattan crosswalk, with bright lights reflected on the rainy and empty street behind him.

The predictable excuse for neglecting pedestrians and cyclists in a given area is that there are so few of them. But wherever walking or cycling is life-threatening, of course, there are few. We urgently need more of both. To get them, we need ways to make MRUs less menacing.

Just as so-called “foolproof highways” invited fast driving, so will CV systems. Just as road design can invite fast driving, so can CV systems. Both tell the driver that it’s safe to drive faster. The systems’ safety benefits for vehicle occupants may be great enough to offset some of the hazards of higher speed, but they have much less to offer walkers and bike riders.

V2X is by far the toughest part of CV plans. Consider the driver who has become accustomed to a CV system that alerts her to pedestrians, both through fixed sensors at intersections and from smartphones that many or most pedestrians carry. This driver’s screen may suggest that there is no pedestrian at the next intersection. With confidence boosted, she may take a legal right on red at a five mph greater speed. Yet a pedestrian may well be there, crossing the street, undetected for innumerable reasons. The five mph difference may well have life-changing significance for this person.

Tech companies, automakers, and even researchers implicitly present CV systems as a means of preserving a status quo that we must change. The typical CV scenarios confirm motordom’s victory in its effort to win priority for drivers in city streets. They reflect the century-old ambition to prioritize motorists’ convenience over others’ rights. Like previous generations of technical innovations in road safety, they make fast driving in cities safer for people in vehicles at a cost to others’ access to streets. They contribute to the deterrence of everything besides driving, thereby pressuring non-drivers to drive. The effects of such pressures are then misrepresented to excuse claims that hardly anyone wants alternatives to driving. V2X systems that would use a walker’s or a cyclist’s phone or equip them with a device force nondrivers to adapt them to environments in which fast driving has been normalized, and leave anyone without such a device unprotected. Just as nondrivers were restricted for the convenience of drivers, such systems protect and preserve fast driving as a fixed given where it should be a variable — especially in cities.

A stock photo of a driver’s hands on a steering wheel.

In cities, CV systems are also likely to endanger pedestrians and cyclists by distracting drivers. In a connected car, traffic data would be presented on a screen that attentive drivers would have to learn to ignore. Hazards would trigger audible alerts, but to prevent false negatives, many of them would have to be false positives, and many others would merely confirm what the driver already sees. Insensitive V2X would falsely reassure drivers, making it dangerous. Sensitive V2X would be a distracting nuisance that drivers would turn off or ignore — making it dangerous too. A V2X system that’s sensitive enough to emit a signal or to slam on the brakes to prevent a collision would have to be sensitive enough to do so when no collision was in store. For drivers, false positives would be annoying. They’d learn to ignore audio signals. Unnecessary automatic braking would be a hazard to other drivers. If drivers could control the system’s sensitivity, most would learn to set it low.

Paradoxically, in cities, V2X would work best when it’s least needed — at low speeds. The slower the car, the more reliably V2X can work, and with the fewest false positives. Yet we know from experience that drivers tend to respond to safety innovations by driving faster. This means that if we adopt V2X at all, we ought to adopt it in tandem with speed-limiting technology. Just as we learned that airbags should supplement seatbelts, not substitute for them, we may also learn that any connected vehicle should also have a speed governor that operates automatically on urban and suburban streets.

CV systems may be an obstacle to the change we need because they treat walking and cycling as exceptional and unexpected street uses that interfere with fast driving. To counteract CV systems’ tendency to invite faster driving, we should condition any introduction of CV systems on the inclusion of speed limitation. By slowing cars down to speeds at which CV systems work better, governors could become an essential component of them. Or we may find that governors make CV systems unnecessary in cities, where speeds limit what any information processor — human or digital — can do in an emergency. Even advanced speed governors are simpler than CV systems, and they may deliver a greater safety benefit.

White light streaks of headlights passing by. A large storage facility stands at the intersection of the major street.

Walkers and bike riders are not necessarily vulnerable. Their vulnerability is circumstantial. It is due, above all, to the speed of the vehicles they must contend with — speed that makes drivers in cities menacing road users. No quantity of infrastructure or technology can reconcile fast vehicles’ hazards with walkers’ and cyclists’ right to the safe and convenient use of their own local streets. By resisting this fact for a century, we have come to accept as normal cities that are so hostile to walking, cycling, and rolling that we imagine that such sustainable, affordable, healthful, and inclusive street uses are too exceptional to be prioritized. They are exceptional only because of a century of failed but costly experiments to accommodate fast drivers in cities. The promises made on behalf of connected vehicle systems threaten to keep us all engaged in continuing the failed experiment, in the worthy hope of saving lives. But as the petitioners in Cincinnati knew a century ago, if we really want to save lives in cities, we must slow vehicles down.

When governments and tech companies promote CV systems, they present fast driving near pedestrians and cyclists as normal, and walking and cycling as exceptional. But a future of equitable, inclusive, affordable, safe, healthful, and above all, sustainable mobility requires that we undo motordom’s century-old effort to ensure that traffic safety policy is committed to making fast driving safer for vehicle occupants, even in cities. If we can slow vehicles down, we can discover that walkers and bike riders are just road users who are not necessarily vulnerable. We need far more streets where walking and cycling are so common that drivers need no automated system to alert them to the unexpected walker or bike rider: because they’re everywhere, they are expected everywhere.

Peter Norton is an associate professor of history in the Department of Engineering and Society at the University of Virginia. He has been a visiting faculty member at the Technical University of Eindhoven in the Netherlands. Norton is the author of Fighting Traffic: The Dawn of the Motor Age in the American City and of Autonorama: The Illusory Promise of High-Tech Driving. He is a winner of the Usher Prize of the Society for the History of Technology and a frequent speaker on the subject of sustainable and equitable urban mobility.



An international journal of traffic safety innovation and the global movement toward Vision Zero published by Transportation Alternatives.

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