Recently, the concept of "complete streets" has gained some political ground. The complete street movement advocates that all streets should be safe and accessible for everyone - regardless of if you're a motorist, a cyclist, or a pedestrian. A complete street tries to encorporate as many features as possible - sidewalks, bicycle lanes, cross walks, and traffic lights - to accommodate every potential mode of transportation that could use that street. While I do agree with the underlying concept of making streets safe and accessible, I am somewhat doubtful that the complete street should be idolized as the ultimate form to base all streets off of.

A complete street tries to accommodate as many modes of transportation as possible on a single street;

The complete streetist's utopian street would include a human lane (a sidewalk), a lane to parallel park on, a bicycle lane, a bus lane, and a car lane - which would then be mirrored on the otherside. However, this brings us to a total ten lanes. The problem with a complete street is that by dedicating a lane to each mode of transportation you tend to end up with very wide streets;

The problem with wide streets is that they take up a lot of space, effectively making them non-places. By using a lot of space themselves they are unnecessarily spacing out the other places around them, making the area around them much less walkable than a human-scale street would;

So a complete street, while having good intentions in wanting to accommodate for pedestrians, may actually be causing more harm due to it's ultra-wide nature, making the area less walkable overall at a human-scale. I'm not suggesting that complete streets are bad, but I do not think they belong as the de-facto form that all streets should be modelled after.

A road without a sidewalk is the worst possible form of road for a complete streetist;

I, too, hate the idea of a steet that does not accommodate for pedestrians. However, for most of history, streets did not have sidewalks;

And if they did it was purely for decoration or some other purpose such as acting as street gutters to prevent flooding during rain. But for the most part, they did not have sidewalks as we know them. There was no need to seperate pedestrians from the rest of the traffic, when the only traffic that existed (except for the occasional animal) were pedestrians. Around the 19th century we began seeing sidewalks typical of today;

I highly doubt they built sidewalks back then for the same reason that they do now. They weren't enough reasons to keep people off the road - there were no cars, and the odd horse didn't pose much of a risk to human life. There are many reasons why they would have wanted sidewalks;

1. Paving around the base of the building made it harder for water and bugs (such as termites) to get under or in the building and cause potential damage.
2. Dirt isn't the most pleasant material to walk on, you didn't want to get your shoes muddy if the ground happened to be wet, and you didn't want dust blowing in through your door all of the time. It was far too expensive to pave the entire road by hand with the technology they had back at that time, so just the area directly infront of the building was paved.
3. During a rain storm, a raised sidewalk would cause the water and mud to drain out on to the road, and prevent it from coming inside as easily as if the entire road was flat.
4. It is also decorative, and much a more pleasant entrance to a building than stepping straight out on to dirt.

Even with sidewalks, the middle of the street was still, historically, a place for people;

The street was a general outdoor public place that could be used for anything - you could use it to ride your bicycle on, children could use it as an outdoor space to play games on, and it was even a popular place of commerce and entertainment, as you could pull up a table in the middle of the street and sell your merchandise to the public or perform magic tricks for passerbyers. Would it have been so wrong back then to build a road without a sidewalk? So what is so wrong with this today?

Many parents would find that outrageous! How could you let your child walk on the road! Let's take this example;

I'm sure the children that live there would walk on the road all the time and nobody would think twice about it. They are both roads with single paved surfaces that cars and pedestrians must share, and no significant form of sidewalk to seperate the two. On both roads there is still the potential for a car to run over you. What is so different about the two that we assume that the first road, which is in the middle of a sparesly populated area that may have a car pass through it a couple of times per hour, is so outragously dangerous that we need to keep people off of it, yet the second road, which is in the middle of a dense residential area that may have a car pass through it each minute, is perfectly acceptable?

The critical difference between the two roads is the scale that they were built at. Because the first road is built at an automobile scale - everything is so spaced apart that you need a car to conveniently navigate it - we tend to assume that the road is only for cars unless there is something around (such as a sidewalk) to explicitly tell us otherwise. The second road is built at a human scale - everything seems to be within walking distance - that we assume that the road is for people. There are no other significant differences between the two roads besides the scales at which they're built. Neither road has enough significant traffic that we need to segregate cars and pedestrians, yet we consider the automobile-scale road too dangerous to share with pedestrians.

This is why I stress that if you build cities at human-scales with human-scale streets you could save yourself a lot of effort of having to build and maintain sidewalks on every side of every road while still being perfectly acceptible, and infact safer, as wide roads encourage speeding.

A shared street, also known as a shared zone or a home zone, is a street where all modes of transportation equally share the entire street;

As an alternative to complete streets, where all modes of transportation have their own dedicated lane, on a shared street all modes of transportation effectively share the same lane. Naturally, cars are encouraged to travel very slowly (usually less than 20 miles per hour) and must give way to pedestrians and cyclists. The main advantage of a shared street over a complete street is that you do not have to waste a lot of space dividing the street into dedicated lanes;

Instead, a shared street can combine this space, allowing the same function as a complete street in accommodating for all modes of transportation, but within a much smaller space;

A complete street takes up a lot of dedicated space that can not be used for anything except for its intended purpose, making it a non-place that unneccessarily spaces out the other places around it. A shared street is a multipurpose outdoor space that can be used for practically anything - just how streets were intended to be used throughout most of history. Most of all, a shared street is more space efficient than complete street, bringing the other places around it much closer together. Shared streets make the entire area around it much more walkable than a complete street could;

Infact, shared streets have been shown to result in fewer accidents as they encourages motorists to be more cautious and drive slower.

I wholeheartedly agree with the basis behind complete streets - every street must be safe and accessible to pedestrians. However, I do not agree with presenting the concept of a complete street as the ideal street, due to the fact that complete streets tend to take up unneccessary space, which has an overall potential of decreasing the walkability of the area. The complete street is a good model to follow if you are retrofitting a city with a lot of arterial roads as they make these streets safe and accessible to pedestrians, opposed to a road that would otherwise only be accessible to cars. But, in all other circumstances, such as commercial downtown areas;

…and residential areas;

…a shared street has considerable advantages in making the area around it much more safe, pleasant, and walkable.

Transitioning to the Traditional City 2: Pooh-poohing the Naysayers by Nathan Lewis is an excellent read. We have to be visionaries and innovators if we want to built great cities.