One-Two-One One-Three-Two

Not one to give up easily, the Mayor of Adelaide, Steven Yarwood, and Adelaide City Council were not prepared to accept all of the negativity and carping about the experimental Sturt Street bike land and after a lengthy period fo thorough consultation, have released plans for proper cycling infrastructure along Frome Road in the city. It actually looks really good. Here's hoping it spreads across the city.

Beginning at South Terrace, the plan is for a complete route all the way to North Terrace using protected bike lanes.

Predictably, the howls of protest did not take long to start and Mayor Yarwood to have to get on the defensive and ask everyone to simmer down a little.

The complaints you hear are predictable and the assumptions behind them generally mistaken. A common gripe comes from what is perceived to be removing space for cars, generally in the form of reducing the number of lanes.

The plan involves Frome Street being reduced from two to one lane, except at intersections where there will be a separate slip lane.

Is reducing the street to one lane really so bad and will it increase congestion? The concept of induced demand suggests no as does the fact that traffic often seems to behave like a liquid. It seems to flow quite well until it reaches a bottleneck of blockage and then you have tailbacks.

Starting at the southern end, Frome Street starts at Carrington Street. That street only has one lane in each direction:


Turning on to Frome Street, it suddenly switches to two lanes:


There is no reason for the change at all other than the fact that there is space for it. That then continues all the way down to the zoo where, because of space restrictions, it reduces back to one:


At certain times of day, that is where you get the bottleneck - exactly as you would expect.

Another bottleneck is at the intersection with North Terrace because of buses turning right. Once Frome Street is reduced to one lane and the bike lanes, there will still be plenty of space to allow for that and even space for buses to have their own lane:


You see this sort of thing all over the place. This is close to the intersection of Main North Road and Fitzroy Terrace - both of them busy and wide roads:



You can see that the single right turning lane turns into three just before the intersection. In fairness, I assume that is so that three short rows of traffic can get around the corner when the light is green to avoid a long tailback. Having said that, once it's around the corner, the traffic is taken the short distance to Prospect Road and then just after that, the three lanes reduce back to two - another bottleneck:


All that happens when a lane is split like that is that there is a mad dash to the front of the queue in each lane followed by ridiculous jossling to get in front once the light turns to green. It slows everyone down. You see it happening every day.

I cannot help thinking that traffic could flow more smoothly (if that is your goal) by avoiding bottlenecks like that. Slow the traffic down to increase road capacity. The new single lane Frome Street will be just fine with a 40 km/h speed limit - and it will be fine with one lane. Slower traffic travelling more smoothly is better for everyone:

You burn the least fuel, and thus pollute the least, when you drive at a slow speed, providing a steady flow of gas to the engine or, even better, coasting. The biggest cause of pollution is the traffic dance of constantly speeding up, slowing down, braking, and idling. In urban areas particularly, the faster the speed limit or the feel of the street, the more starting and stopping drivers do. When traffic speeds slow down overall, the flow becomes smoother, and the result is less pollution.

It is also of course a lot less stressful. I have heard that heart attacks are not all that comfortable so if we can avoid them, all the better.