Thursday, 14 January 2016

Road hierarchy

Our road hierarchy is in a big mess in newer developments. And in the older areas too, but newer developments is the focus.

It has several levels. Alleyways are less common in newer areas, but they still exist. Local access roads give direct access to homes and shops, and they usually have parking on both sides and depending on the road, usually enough width for two cars to pass, but lanes are undefined, collector roads take traffic from the homes and puts them onto arteries, and they usually have things like shops, homes, schools and other destinations on them. These have 50 km/h speed limits, as do local roads, they usually have parking on at least one side of the road, generally both, and two lanes for motor vehicle traffic, they may have bike lanes or sidepaths but this is less common. Intersections are with other collectors generally stop sign controlled or traffic light controlled.

Arterials usually have 60 km/h speed limits, though 50 limits are used in a number of arteries, sometimes 70 is used, they have 2 lanes to start with plus turning lanes, and they usually end up with 2 or 3 lanes per direction, a divide between the two directions and turning lanes, though a few stretches have bidirectional centre left turning lanes. Intersections are usually traffic light controlled, some have stop signs in the interim 2 lane stage, and they continue to have stop signs for very minor side streets and for business accesses sometimes, and they usually have no homes on the street but do have some shops and business accesses to parking lots. And of course we have the freeways, limited to 80 and 110 km/h, divided, grade separated, with at least 2 lanes per direction and a shoulder.

The Dutch don't like this confusion between types of roads. They make it very clear from roadway design what kind of street you're on. In my view I would like to make collector roads either access roads or take out the buildings directly adjacent to street oriented roads, but neither is quite right. I will be pragmatic, but I will try to get as close to the functionality, predictability and homogeneity of roads as possible.

Local access roads have 30 km/h speed limits, may or may not have parking, but does give direct access to the homes and businesses. The intersections are either yield sign controlled for intersecting with distributor roads or uncontrolled for intersecting with the other local roads.

What we generally call collector roads will be distributor roads. These will have as little parking as possible, and will have cycle lanes or cycle paths, the latter hopefully being more prevalent, and have intersections controlled by yield signs with local roads and sometimes other distributors, and roundabouts with most distributor-distributor road intersections. Bus routes should be routed on these, although preferably outside of neighbourhoods when possible. They will be one lane per direction roadways with single lane roundabouts and at signalized intersections, there will be one lane for each direction it is possible to proceed in.

The arterials are classed as either a distributor road or through road. Through roads carry vast amounts of traffic at high speed with a high flow rate, linking entire districts in the city. Freeways are preferable for this task, but 50-70 km/h arterials will also do the trick. If a road is classed as a through road, the speed limit is upgraded to 70 km/h when possible, left turns lanes are channelized, the road is grade separated where possible, and is generally equipped with 2 lanes per direction and a median between the two directions is added. Roundabouts like turbo roundabouts are also added where possible when grade separation is not feasible.

Distributors take traffic at medium speeds at medium flow rates. Many arterials fall into this category. They will be downgraded to single lane per direction, with a divide between the two directions, certainly a bicycling path, though sidewalk presence or not is less certain. Bus routes are routed on these when possible, and also when possible, they have a completely separate busway, usually bidirectional, usually in the middle of the road when possible but also might be on one side or the other. The speed limit is downgraded to 50 km/h, a cycle path is either added or modernized, and intersections are governed either with traffic lights, yield signs or roundabouts, the latter when possible. Things to naturally slow the speeds, narrowed lanes, raised tables, a median refuge requiring traffic to go right and then left in a more sudden movement, and a dashed line on the side of the road optically narrowing the road is added.

Freeways are generally not upgraded much, though interchanges that are not free flowing ones have roundabouts added to the remaining at grade intersection(s), they may also have an HOV lane added, extended where it's sensible to do that, a guardrail in the middle of some sort, even a cable barrier, is added when possible. Electronic management systems are added when possible, even just ramp signals on the entrance ramps on non systems interchanges. The speed limit should be as close to 130 km/h as possible. In some cases this can be done right now, others it might take certain upgrades like on Whitemud Drive, updating the interchange ramps, maybe making more use of collector roads that collect traffic from side streets. When driving speed is naturally enforced, at 130 km/h this can be done just by having drivers being comfortable on their own at 130, or in congested freeways, 80 km/h perhaps, it works better.

All this makes it very clear what the difference is between this road:,5.4916832,3a,75y,232.71h,86.15t/data=!3m6!1e1!3m4!1sjotx4St0GFhZ9hRSvmBjuw!2e0!7i13312!8i6656?hl=en,

this road,,5.5024503,3a,44.5y,315.33h,82.83t/data=!3m6!1e1!3m4!1sCjlBZGXNi09mNF3TRVD2xA!2e0!7i13312!8i6656?hl=en,

this road,,6.5311089,3a,90y,129.54h,78.71t/data=!3m6!1e1!3m4!1sMlV0DkoQuv8Mpnl2WZs8rQ!2e0!7i13312!8i6656?hl=en,

and this kind of road:,6.504729,3a,90y,86.94h,80.27t/data=!3m6!1e1!3m4!1s0hVBGawn7gr4_4Dy7okcQQ!2e0!7i13312!8i6656?hl=en.

It's what leads to less confusion, fewer collisions and more effective roads.

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