Traffic Engineers, We Need You

Traffic engineers: the world is changing, and so have the objectives of your job. For the last century, we have called on you to optimize vehicle travel through urban transportation networks. Now, in the midst of a global pandemic, with traffic volumes at half or less and stricter social distancing requirements with each passing day, the service that you provide to cities needs to change.

The top goal for societies and governments right now is to curb the spread of COVID-19. Traffic engineers have jurisdiction over an overwhelming amount of public space, and as such, you have potential to play a heroic role in reducing the spread. Transmission isn’t occurring between motorists; it’s occurring between pedestrians – those folks who are unable to obey two-metre social distancing requirements because they’re crammed onto 1.8-metre sidewalks.

In other words, we need you for an entirely different purpose than you’ve known since the beginning of your profession nearly a century ago. Will you rise to the challenge?

While traditionally, your role has been to manage vehicular congestion and delays, in this time of crisis, your new top objectives should be:

  • Minimize opportunities for transmission of the virus on streets and at intersections
  • Minimize the burden on the healthcare system caused by motor vehicle collisions

Below I present three simple actions that all traffic engineers have the ability to implement to address these objectives.

Override the “beg buttons”

Most intersections are equipped with pedestrian crossing signals, but many require pedestrians to physically push a button to get a walk signal. This has two major problems.

First, these “beg buttons” are a frequently-touched surface by many hands in a day, an ideal transmission point for germs and especially the COVID-19 virus, which can survive on metal surfaces for up to three days. Cities are closing playgrounds and upping their sanitation practices for exactly this reason – to reduce the potential for the virus to spread through surfaces.

Second, since traffic signals are often coordinated with each other, “beg buttons” require a pedestrian to be at the crossing at the right time in order to get a crossing. Missing the opportunity to cross in a coordinated signal cycle means waiting at a corner for even longer. Waiting at a corner for longer means an increased chance a pedestrian will come into contact with another person.

This crossing does not provide a pedestrian walk signal by default and this pedestrian did not reach the push button in time to get a crossing.

Overriding “beg buttons” to provide pedestrian crossings by default is seen as a detriment to the smooth, efficient flow of traffic. Sure, it’s a loss of “green time” that could be provided to motor vehicles. But under the new traffic engineering objectives, this is exactly what is needed to reduce transmission of the virus.

Call to Action: Modify intersections to always display pedestrian walk phases by default, without requiring the pushing of a button.

Reduce signal cycle lengths

The cycle length of an intersection is the time it takes for that signal to go through the green movements for all directions of traffic (the time it takes to “repeat itself”). Cycle lengths typically range from 60 to 140 seconds, with longer cycle lengths providing more vehicular capacity. But anyone who’s waited what seems like forever to cross a busy intersection knows that longer cycle lengths increase delay for pedestrians.

At a compact urban intersection with a cycle length of 60 seconds, pedestrians have to wait on average 15 seconds to cross. At a large suburban intersection with signalized left turns for vehicles and a cycle length of 140 seconds, that waiting time increases to 50 seconds, nearly a full minute.

Every additional second that a pedestrian waits at an intersection to cross is more time for crowds of people to form at corners. Crowds of people means more transmission of the virus.

More crowding occurs when pedestrians have to wait longer to cross intersections

One of the best things a traffic engineer can do right now to help public health is to reduce signal cycle lengths. Cycle lengths of 60-90 seconds are ideal for urban areas. All it takes is a simple reprogramming – no physical infrastructure. The cost-benefit of this is huge.

Call to Action: Reprogram traffic signals to operate on the shortest feasible cycle lengths.

Reduce vehicle speeds

Less congestion on roadways is leading to higher rates of speeding. Toronto is already seeing this, with a 30% increase in speeding tickets and a more-than-doubling in stunt driving charges despite traffic volumes being down 50% or more on many streets. These dangerous behaviours are entirely unnecessary and place a higher burden on our increasingly-strained healthcare system.

Traffic engineers don’t entirely control the speed at which motorists travel – road design and enforcement play major roles too – but they do have the ability to influence speeding. Along major roadways, traffic signals are often coordinated so that large groups of vehicles (“platoons”) can move from intersection to intersection with a steady stream of green lights. This is most obvious on one-way streets but it is done one two-way streets too.

These coordinated signal timing plans assume a certain travel speed for motorists, which can be adjusted. Portland, Oregon, for example coordinates its entire downtown street traffic signal network to just 30 km/h (20 mph) vehicle travel speeds. The result is an environment that is much safer for all road users.

In other words, by changing how signals are coordinated, traffic engineers can influence the speeds that motorists travel.

This one runs counter-intuitive to the traditional objectives of a traffic engineer as well. Faster vehicle speeds means shorter travel times, which makes for a good vehicular transportation network. But efficient motor vehicle travel is the least of our concerns now. With speeding on the rise, we need to curb the potential for more people being sent to hospital from traffic collisions.

Call to Action: Reduce the speeds for which corridors are coordinated, or even better, remove coordination entirely, to reduce potential for motorists speeding.

Traffic engineers, we need you. But not for your traditional role of optimizing traffic flow. We need you to do your part for getting us through this pandemic. We need you to exercise the tremendous control you have over our streets to help reduce transmission of COVID-19 and reduce the burden of traffic collisions on the healthcare system. You have potential to be heroes to society in our time of need and save thousands if not millions of lives. Will you rise to the call?


  1. Have an independent light just for pedestrians ONLY. During which, NO vehicles including bicycles should be making left , right turn or going strait through during the pedestrian crossing.


  2. I’m a traffic signal engineer, in Oregon. What works in downtown Portland does not work for traffic lights on state highways. Portland has many pedestrians and cyclists, but on state highways they are few and far between. Recalling the pedestrian service is extremely inefficient if you don’t have pedestrians. That’s not going to happen. I hate having to push the button too, it should only require waving a hand and not physically touching, we just haven’t done that yet. There are cameras that detect pedestrians at some locations. Lastly, removing coordination would cause gridlock stop and go traffic, which is more dangerous for everyone because it increases wrecks. When working on coordinated lights, this is very obvious when you’re making adjustments and one is out of step.


    1. Thanks for your comment. My post was not suggesting to break coordination, but rather to lower the speed for which signals are coordinated. I’m not sure how it’s done elsewhere but where I live, major-minor street signals will have long cycles and long green times for the major street, making it easy to speed through all of them. Peter Furth published some interesting research on how to use coordination as a tool to mitigate speeding opportunities that I would love to see implemented:

      Curious to know your thoughts on that.


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