Monday, 21 March 2016

Sustainable Safety: A thorough look into each of the 5 principles. Part 3: Predictability

There are a few ways that roads can be more predictable and have more predictable traffic of all kinds using them, and when you know what is expected of you and what you can expect of others, then everyone will know what to do, when, or at least know it better than they do now.

The roadway design must make it predictable what you are going to find on a road and what sort of regulations and behavior is expected. Many times some collector roads look like arterial roads, and the other way around. 40 Ave is hard to distinguish from an arterial road, especially if few are parking on the road when you are using it. Many times collector roads look like large access roads. Other times, you can't even tell the difference between a built up area and a rural area because of a lack of a clear definition between them. A median that requires that you go in a sharp S curve, go over a speed table and then you pass a sign that says "name of municipality. Speed limit: 30/50 km/h", then you are on a road with concrete curbs on either side, makes it very clear what kind of street you're on.

By making only full motorways having a wide paved shoulder, then you can more accurately predict whether you are on a wide autoweg or are on a motorway. Often times I have no idea about whether the roadway is like this or not. Other examples include that many cities in Alberta and most other countries post either 60 km/h or 35 mph speed limits on urban arterial roadways, but some roads that are slightly older, 51 Ave for example in Edmonton, don't have 60 km/h speed limits. How am I supposed to know which kind of limit to apply where if for some reason I miss the sign? The speed of traffic is no help, it is very easy to speed in Edmonton and I have no way to know whether the traffic is going at the speed limit or whether it is speeding without knowing the speed limit, going at it and pacing the traffic.

The Dutch tie a lot of things together. If you are on a road with brick paving, car parking in dedicated bays, you don't see a separate cycle path and sometimes neither a sidewalk, and there are buildings that affront the roadway, you know that this is a 30 km/h area and should expect to see cyclists mixing with traffic and that you must go no faster than 30 km/h. If you are on a roadway that has at least 2 lanes in each direction, a guardrail and a verge between the two directions, a hard shoulder at least on the right side and you had to get on the road via interchanges, you know that you are on a motorway, even if you didn't see the sign. If you are on a road without much development nearby, separate cycling paths or a service road, there are a pair of continuous centre lines and a dashed white edge line, and are in the rural area, you know that you are on a rural distributor and can go up to 70 km/h (80 in the Netherlands).

When you approach an intersection, the approach will be very clear. Often it will be a roundabout if you are on a distributor road, exiting an interchange or are exiting the 30 km/h zone (indicated by a change in surface from brick to asphalt, the cyclists having a transition into a cycle path, and a few other clues). If you do encounter traffic lights, then the design will also be very clear. A single signal head above each lane, separate controls for the different directions you can go in, and a physical design that closely resembles how a non traffic light sign controlled intersection would look (if the traffic lights go out for any reason, then how else can you expect the intersection to work at all?). As few intersection designs as possible are used, so as to make it easier to have a mental list of what you need to do at each kind.

The behavior of other road users is assisted by this predictability. By creating natural reasons to obey the rules that apply to each road user, for example someone that is expected to give the right of way to someone else will usually encounter things like an increase or decrease in elevation and sharp corner radii. Stop signs are rarely used, partly because using them on mass and places other than where the visibility is so low as to require them creates a lack of predictable behavior because you have no idea whether the person facing the stop sign will obey it or not. When safe behavior feels like natural behavior, safety is greatly improved.

Laws must be logical and easy to understand why you would create such a law for the purpose it was created for. This also applies to signage and regulations. It is easy to understand why you should not go 130 km/h in a 30 km/h school zone. When you face a speed table, tight corner radii, clear yield signs and the markings and physical design from the main road continuing on as if nothing happened (think how a driveway is usually built over a sidewalk in new developments in Edmonton), then yielding becomes logical and easy to understand. This again creates predictable behavior.

The physical design has other ways of making behavior predictable. The roundabout has another thing to make it easy to understand, both by cyclists and pedestrians and also by motor vehicles. When you are in a car, approaching a single lane roundabout, you only ever need to look to the left to see if there is traffic that you must wait for. And you only ever need to look to the right to see if the traffic will yield to you. With wider median refuges and tight corner radii on the exit of roundabouts as well, it is easier to know whether traffic will exit or not, even if they don't use their turn signals. This makes it far more predictable as to who is doing what, when and where. Cyclists and pedestrians also benefit. It is easy to know what direction to look at to see where the traffic is coming from. You look towards the roundabout to see the traffic coming from the roundabout and you look at the approach arm to see where the traffic from the approach is. And being able to do this fairly far away from the main roundabout and on completely separate paths with plenty of room to divide all of your tasks into easy to follow algorithms makes it easy to know what to do, when, and where.

People often talk about cyclists being unpredictable. Well, this is because the rules applying to them and where they should cycle is not often logical, is not easy to explain and yes, education could be improved. If you don't provide cyclists with a separate path when they feel intimidated by the traffic, where would any reasonable person expect them to be if there is a sidewalk? On the sidewalk away from motor traffic in almost all cases. And if you are a motorist and expect this, only to find a cyclist on the road by surprise, this can be a very dangerous situation. When the traffic light delays are excessive and pointless, and especially when the "flow of traffic" is being prioritized, then people will cross on a red light. If you give a cyclist a sidepath but don't make the intersection design the way the Dutch do, with cyclists having their own specific crossing, signals if applicable and signage, markings and other cues like continuous surface of the cycleway over the side road, then expect unpredictable behavior because there is nothing to suggest what to do if the sidepath suddenly becomes a sidewalk for whatever reason.

We have a lot to do if we want to make roadway design, laws and actual behavior predictable. I recommend this article for another overview and for more information: I hope to see you back for part 4: forgiving road design.

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