Sunday, May 3, 2015

Sidewalks and driveways: is it time to throw the curb to the curb?

So a few months back, I saw a Tweet regarding the issue of driveways that made me think, and I put it aside in order to write on the subject later on. The time I think has come, so here it goes.

First, here is the Tweet:
Later on in the discussion, this image was brought up as an example of the horror of driveways:
Proposed townhouses with massive driveways
That's a pretty strong statement. Driveways are the most anti-urban thing, really?

Reasoning behind the claim

The claim is essentially based on a North American conception of the street and integral mode separation, wherein motorized vehicles and pedestrians need to be strictly separated (and sometimes cyclists are added in there too). In such a perspective, an area without sidewalk is necessarily pedestrian-hostile and thus anti-urban because it forces pedestrians in an area made for cars: the street. I've already spoken about this conception in an earlier post.

What is the link between that conception and driveways? The problem here is that driveways represent an intrusion of cars into the pedestrian corridor and breaks it off in disconnected pieces. On the other hand, if cars are parked on the street instead, then the pedestrian corridor is safe from intrusions by cars.
Schematic representation of the scenario with on-street parking
Schematic representation of the scenario with driveways
Of course, cars intrude on these spaces only rarely, it isn't a commercial parking lot where cars stay only 30 minutes or so, and they do so only at very low speeds, so how bad is it really? There is also the issue that pedestrians are then asked to walk between parked vehicles and moving vehicles, though, to be fair, vehicles parked on a driveway tend to be some distance away from the sidewalk.

I think what mainly compounds the problem is the curb cut. Sidewalks are by tradition built slightly elevated from the street (the curb), as a result, the sidewalk is lowered at least partly to the level of the street to allow cars an easier access to the driveway. Since North American sidewalks are so narrow, it often means that the pedestrian corridor will not be level, but will have many sections where it is lower and in a slope, making it much less comfortable for pedestrians.
Example of curb cut

Why have a curb anyway?

If the curb cut is so annoying for pedestrians, one might ask why we have a curb anyway. It's not like this tiny elevation is going to do anything to stop cars with 150 to 300 hp from going on the sidewalk. Not one month goes past without some car somewhere "jumping the curb" and hitting pedestrians or, more rarely, houses. If the curb is meant to protect pedestrians from cars, it is failing badly at it. At best, it keeps cars parked on the street from parking on the sidewalk... sometimes. Way back, when the vehicles in the street were horse-drawn, it may have been a significant obstacle (and indeed, major Roman streets did have sidewalks), but horse-drawn vehicles weren't that much of a threat to pedestrians.

In the end, perhaps the prime reason that sidewalks were invented wasn't about safety, but about cleanliness. When roads were unpaved and horses and beasts of burden were in common use, the road itself could be extremely dirty. Muddy when it rained, with pieces of feces from animals, not the best area to walk in. Sidewalks were often built first, often in wooden planks (in which case they are often called boardwalks) in order to provide a clean way of walking around. To avoid accumulation of water in the absence of sewer systems and to avoid dirt from the street from being blown over, they were elevated. The road was still for pedestrians, but those who wanted to get around without fear of being dirty on arrival could use sidewalks

So with universal street paving, the replacement of beasts of burden by motor vehicles and rainwater collection systems, the reasons for the curb's existence don't seem all that significant nowadays. If we get rid of the curb, then we don't have curb cuts and driveways can be way more tolerable for pedestrians. And indeed, I will point out again Japanese streets that are built without a curb. The Japanese also hate on-street parking and make massive use of off-street garages, parking lots and driveways:
Commercial street in Takayama, note the small water channel to drain the street, a traditional method that works well

Recent developments in Yokohama, with no sidewalk and pedestrians owning the street, driveways are massively used and often decorated, not disturbing pedestrians in the least

Another residential street, note again the parking in the form of driveways to the left

One last example from Tokyo, note the garage doors to the left, again, they do not make it less comfortable to walk thanks to the absence of a curb
But for residential streets to work in that way, it is necessary that they be built primarily for pedestrians, not cars, and car drivers need to feel that they do not belong there so that they drive slowly and carefully, like in a parking lot. So when pedestrians and cars have to share the same space, that space must be NARROW with fixed objects close to the edges (trees, walls, fences, etc...). Too often, I've seen residential streets in North America being built wide without sidewalk, probably with the thinking that if cars and pedestrians have to share the pavement, then it needs to be wider to provide greater separation, which is exactly the opposite of what we should do.

On arterials where we want to channel motorized traffic, use separation is still required. If you want cars to go fast (and I define fast as anything above 30 km/h, about 20 mph, and I'm probably overestimating it), then you need to clearly separate vehicles and pedestrians. But again, the curb is a terrible way to do so, it is not much better than a line, only useful to drivers to align their trajectory when going fast.
The sidewalk acts like a big line to aim a car's trajectory...
However, as it is low to the ground, it is invisible to a driver looking to the side
The Japanese, again, seem to have this down better than us. When they have sidewalks, they favor fixed obstacles at the limit between car space and sidewalk, and if they have a curb, it is often only the slightest of curb or even just present at the border between sidewalk and street, to provide an indication for cars when they're driving too near to the sidewalk. That way, curb cuts have little to no impact on pedestrians who still have access to a flat, continuous path.
A Japanese sidewalk with a curb cut for a parking lot. The sidewalk and street are separate by trees and planters otherwise, there is also a tiny curb, but the pedestrian corridor is far enough that it is largely unaffected by it.
Japanese sidewalk in Akihabara, note how it is essentially flat with the street, but with small poles separating the two, a much more effective separation
Sidewalk in a recent area of Yokohama, again using trees and small poles to separate the sidewalk from the street, the sidewalk being almost level to the street. You can see parked cars in parking lots, which entries again require no curb cut, simply an absence of pole or tree.
Example of a curb used to separate street and sidewalk, but the curb itself is just 15-cm wide or so (6 inches), it can be interrupted for drains or for driveways and parking lot entries (yes, a few eccentric Japanese own Jeep SUVs in Japan). This case is particularly interesting because of how similar it is to North American examples (sidewalk width, manhole, etc...)

In defense of driveways and parking lots

Some may ask why bother with making curb cuts less disruptive, when we could just not need them by avoiding driveways. The attraction of driveways is actually that it is a very spatially efficient way of inserting parking in an area. Parked cars require space when immobile, yes, but they also need maneuvering space so the driver can drive into that spot and leave it. Like on-street parking, driveways use the street as a maneuvering space, but unlike on-street parking, it requires only about 2,5 meters of width on the street (8 feet) versus 6 meters for cars parked on the street (20 feet), and you can have a driveway deep enough for two vehicles. So that means that driveways can pack nearly 6 times more cars than on-street parking in the same street length... by sacrificing the front yard of course.
This may not look good, but it manages to pack 12 parking spaces in a 25 meters x 35 meters lot (85 feet x 120 feet), to do the same with on-street parking, you would need nearly 100 meters of road (330 feet). Like the aesthetic or not, it remains very efficient, all without having expensive underground parking.
Driveways well-integrated in front yards in Japan, leaving the street uncluttered with cars for the benefit of pedestrians and cyclists
Again, people may ask why bother with packing parking spots efficiently and affordably... Well I agree, but unfortunately, in many places there are still strict minimum parking requirements which limit the number of units that can be built to the number of parking spots that can be built (sometimes with a 1 to 2 ratio). In that context, being able to pack more parking more efficiently can allow for more density, and doing it cheaper makes dense housing less expensive to build. Of course, it's not the best outcome, not at all, but it may be the best we can do in many areas, a necessary first step for more sensible urbanism.
Due to Houston's strident parking minimums, without driveways, townhouses like these would be impossible to build and possible density would be half or less of what is currently being built there.
Another alternative might be to have small parking lots in residential areas, which allows to reduce the curb cuts required and provides great spatial efficiency. The parking lot could also be hidden by trees or small fences to reduce their visual impact on a neighborhood. If one is under-used, it could also be converted to a building.


Yes, driveways are anti-urban... in a certain model of urbanism in which all streets (bare perhaps a few exceptions) are built primarily or exclusively for cars, with pedestrians relegated to small sidewalks. In that instance, protecting the sidewalk from frequent curb cuts and from cars intruding into their narrow corridor does make sense. However, we must keep in mind that this isn't the only model. The Japanese and other Asians provide a different model where residential streets are primarily built for pedestrians and cyclists, so that car drivers feel unwelcome there. In that model, driveways and other off-street parking allows the street to remain uncluttered and welcoming for humans. This is the concept of "shared space" that some have been experimenting with but that have been in use for decades in many Asian countries.
Shared space in the Netherlands
Maybe we simply need to review entirely how we treat pedestrians in North America, and Europe too. We keep building ugly, narrow sidewalks of segmented concrete blocks everywhere when most of the rationale for their existence (muddy, filthy streets, poor drainage of rainwater) is gone. Maybe we should just build a lot less of them and build shared streets instead where cars are allowed but unwelcome, but when sidewalks are required because of street width and vehicle speed (arterials), they should be built wide and to a good standard of quality so as to be welcoming and comfortable to pedestrians.


  1. Yes! Driveways are really not that bad if they're rarely used. And in terms of how the street feels, I much prefer not to have parked cars. They make things so much more dangerous when people try to cross the street and nobody can see them behind some giant SUV. They also make things more dangerous for cyclists on the street with the potential of being doored, and the potential to suddenly pull out or even make a U turn right in front of a cyclist (I find the expression "flip a bitch" particularly apt for the sudden unexpected violence such a maneuver can have).

  2. This comment has been removed by a blog administrator.

  3. Interesting read. On the curb (at least 6-8"), I would contend that you're missing the physiological impacts it has both on drivers (hopefully forcing them to drive slower and cautiously) and pedestrians knowing that a driver really doesn't want to hit that curb, regardless of whether they are there or not.

    I think the real issue is access management (too many curb cuts, etc.), not the curb itself.

  4. The curbless scenario is of course even more superior for wheelchair users or any pedestrian wheeling something (strollers, etc). The frequent changes in slope combined with the tendency of cars to park in driveways while blocking the sidewalk makes wheeling anything a real obstacle course

  5. This comment has been removed by the author.

    1. The theory that sidewalks with a high curb are a hangover from previous needs makes sense to me. I keep wondering why we continue with them due to the issues they create for anyone using wheels and the arduousness of adding curb cuts. Wouldn't it be easier just to skip the high curb to begin with? If water flow is an issue a subtle beveled threshold to the street could still be effective. Bollards seem like the best solution if a street space is too busy with cars to use the shared space deign.
      (I adjusted my profile so that it would not show as "unknown")