Post-it notes at a makeshift memorial for the victims of the June 3, 2017 terrorist attack in London. Image by Algorithms Riven licensed under Creative Commons.

On Tuesday afternoon, 29-year-old Sayfullo Saipov intentionally drove his rented pickup truck into popular protected bikeway in lower Manhattan, killing eight people and injuring a dozen others. Sadly, it's just the latest incident of a vehicle-wielding terrorist attack.

In Charlottesville this past August, a white supremacist terrorist killed one woman and injured 35 others when he drove his car into a crowd of protesters, and similar attacks have taken place in Barcelona, London, Berlin, and Nice.

Many local urbanists are excited about the possibility of an 18th Street pedestrian zone, and advocate for more walking and biking infrastructure more generally. However, this slew of horrific incidents where terrorists drove vehicles into unprotected people on bike or on foot has sparked the question: How should urbanists respond to this reality? Our contributors weighed in.

David Cranor found the area where the New York terrorist entered the bikeway:

This is where the terrorist in the recent New York bikeway attack entered the trail. Image by Google Maps.

We shouldn't spend extra money to terrorism-proof every trail, but we can probably make them harder to attack (and to accidentally drive on) with some small changes. We probably only need to worry about a few trails, and on those we can design them with planters that create chokepoints at places where a car might enter.

This is where he got on the Greenway. This is a pretty large driveway.

If you put a bollard or some other sort of raised median where the double yellow line median closest to the street is (between West Street and the trail) it would become very difficult for a truck to make that turn. There are already bollards or posts at most of the corners (thought the one on the near right could be positioned better), which is what I was talking about, so not much would need to be moved there.  This would also lead to some traffic calming I suspect.

Another alternative would be to add some sort of gateway above the trail. Low enough to not impact people, but high enough to stop a large truck.

Maxime Devilliers says,

Liverpool, England, has done a particularly good job of enabling pedestrian zones at certain hours of the day throughout the city centre without the need of any police intervention and that are fully automated. I really enjoyed them and thought they did not hinder the public space/view shed at all. Jersey barriers and vehicular walls are hideous in comparison.

However, we should not plan for intentional attacks because it simply hinders the public space (see the south side of the White House for example). Terrorists will sadly usually find a way to circumvent protective barriers.

In some cases, such as for street festivals or protests, police park their cars across intersections to make it more difficult to drive a vehicle into the crowd.

Gordon Chaffin says,

Protected bike lanes and pedestrian areas are necessary specifically because they prevent incursion from automobiles.

In the cycling and pro-pedestrian space communities, we are often beggars trying not to be choosers when we get new bike lanes and public space reclaimed from automobile-dominated road spaces. However, we need to be more insistent that design elements incorporate protection measures against cars. The everyday differences in physics (speed, weight, etc.) of car traffic and cycling/walking traffic present far greater dangers than terrorism.

You should build bike lanes. You should build them with raised concrete medians or bollards. You should do so because more people die every day from crashes. If the political will comes more from terrorism, I'm not going to complain. But, parking police cars as temporary barriers isn't a solution to anything.

Payton Chung notes that statistically, terrorist attacks aren't a leading cause of death and injury.

Echoing the helmet debate, many more die from a lack of physical activity. Bikeways lead to more people bicycling, and more people integrating low-impact physical activity into their daily routines–perhaps the easiest way to maintain cardiovascular health. Fewer bikeways means fewer people biking, and more people dying premature deaths due to heart disease or metabolic syndrome.

Patrick Kennedy pointed out that this isn't an all-or-nothing proposition.

You can't fortify every target–but perhaps some bike infrastructure should be prioritized for physical reinforcement based on its prominence and/or the number of users. This particular path in New York is very heavily used and passes through very prominent locations, so it makes sense to me that it be reinforced.

In our area, perhaps you could make the case for the Penn Ave lanes–understanding that all elements have to be removable for the inaugural parade–and maybe the section of 15th Street around where it doglegs near the White House.

On the other hand, most lanes like the one on New Mexico Avenue bike lane probably aren't at risk of becoming a terrorist target–unless some neighbor is still particularly aggrieved over its installation.

Finally, Travis Maiers says:

No question this was a terrible event, and there could be lessons for the future. Unfortunately, we’ll never be able to make our roads 100 percent terror-proof.

Lining every busy sidewalk and bike path with bollards and gates just isn’t feasible. But I do think that many of the design elements of Vision Zero infrastructure, apart from making streets safer for everyone everyday, can help prevent these kinds of events. We should keep working toward that goal.