Porsche 908 in Prince of Monaco's car collection

Engineering over enforcement

How urban design can inform digital products

In my introductory physics class, we replicated calculations by the Nobel Prize-winning physicist after whom our department was named. After returning from the Manhattan Project, this professor became frustrated by a common problem at the university and set about fixing it with physics. His invention worked and is now found ubiquitously on campus - and worldwide. The issue was speeding cars, and his invention was a speed bump. Drivers can ignore a speed limit but can’t miss a speed bump.

I live in NYC, a city that announced a “Vision Zero” initiative in 2014 seeking to end pedestrian deaths from cars. In the almost decade since, the pledge has meant more marketing than results. For instance, the city requires every Uber to “have a Vision Zero Sticker on the windshield to pass inspection.” I assumed that “Vision Zero” was a political talking point rather than an achievable reality - until I went to Oslo.

Oslo is somewhat tiny, comparable in population to Denver (9 pedestrian deaths in 2022) or Memphis (83 pedestrian deaths in 2022). Yet, since 2019, Oslo has had zero pedestrian deaths from cars and zero bicycle deaths.

Oslo became a safe city for pedestrians and cyclists by doing more than mandating stickers in Ubers. While there last month, I researched more about how they achieved such a safe city. I found a mental model that applies to more than city planning - “Engineering Over Enforcement.”

Enforcement philosophy is rooted in the idea that behavior can be controlled by threatening punishments. Engineering philosophy believes that infrastructure can be designed to incentivize desired behavior. When Oslo sought to reduce pedestrian deaths, it turned to engineers.

Traffic intersections are a typical and illustrative example of how somebody can apply different philosophies.

Traffic lights are an example of enforcement - when a signal is red, nothing physically stops a car from going through the intersection. The only thing enforcing proper behavior is the fear of a crash or a ticket. When rules get broken at traffic lights, the resulting accidents tend to be high-speed T-bone crashes that can easily prove fatal. People used to traffic lights may think that the way they work seems reasonably obvious, but Americans may be surprised to learn that “right turn on red” is illegal in most of Europe (and in NYC). “Red means stops, green means go” may also seem simple, yet it fails for the colorblind - and one in twelve men is red-green colorblind. Traffic lights are not as legible as they may appear.

When enforcement doesn’t achieve its desired outcome, the only option is more enforcement. New York City began automating red light enforcement with cameras in 1994 to try to curb the problem of drivers ignoring the rules of intersections. Yet, in 2022 - the city cameras issued 618,000 red light violation tickets - showing that enforcement often fails to eliminate the problem.

Roundabouts serve the same function as traffic lights but follow an engineering philosophy in their design. Roundabouts can be confusing to first-time drivers, but that’s a benefit. People slow down, maintain awareness, and can understand the basic rules intuitively. It’s simple – “slow down because your path is blocked, and merge when there’s space.” This engineering means that accidents tend to happen less often in roundabouts, and the ones that do occur tend to be low-speed fender-benders. Plus, roundabouts work without electricity, are faster for drivers, and don’t rely on ticket-sending robots.

Intersections are one small example where philosophies can diverge. But, as I learned in Oslo, engineers have a whole toolkit of methods to make cities safer. Bumping out a curb slows down turning speeds and protects pedestrians. Bike lanes can be safer by being raised above the street instead of relying on a painted barrier. Limiting how far cars can see ahead of them slows them down. Behavior can be designed rather than just enforced, and in aggregate these small changes can make a city safer.

I found that as a pedestrian, Oslo felt pleasant. I didn’t need to look for as many signs to avoid getting hit by a car. Crosswalks were easier to navigate. But, at the same time, the city didn’t feel rule-heavy – there were areas where the city chose an enforcement philosophy over an engineering one. For instance, the NYC subway uses fare gates (engineering!) to ensure riders pay. But, in Oslo, the metro had no gate - I could board the train unencumbered, and occasional fare inspectors enforced tickets. I think enforcement works best when most people follow the rules, and you don’t want to impede everybody to correct a few outliers needlessly.

My takeaway from the “Engineering Over Enforcement” philosophy is that rules must be obvious. Whether you’re building a road or an application, assume that most people will not read or pay attention to the terms. People are distracted by push notifications, chat messages, emails, phone calls, music, and more - so you probably don’t have their full attention while they are using your product. (And, unfortunately, the same is true while people are driving).

Looking back, it turns out that I learned the benefits of engineering over enforcement many times while building Moonlight, an engineering marketplace. We originally made our money by charging a success fee upon hiring somebody through the website. But, people would often claim ignorance of the fee after making a hire. We even tried including an e-sign contract for companies in their signup process to make it evident that we were entering a legal relationship - and people would still later claim not to know the rules. I wrote in the past that “suing customers isn’t a viable growth strategy,” and we followed this at Moonlight by switching from enforcing a success fee to engineering an upfront subscription before accessing candidates. Users found this approach more legible, and changing to a subscription led to a 300% increase in revenue.

The next time you cross a speed bump, slow down and appreciate that it’s an elegant engineering approach to control speeds. It doesn’t take police, laws, signs, or robotic camera machines to control speed. It’s universal of design standards and unit of measurement. And, it makes for a fun homework assignment in physics class.

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