General Road and Highway Discussion

[ijmorlan]

I’m just gonna sneak in here and casually mention that adding more lanes doesn’t equal less congestion

Thanks, bye

True in general, but in some cases it does. To take an extreme example, imagine you have a six lane road, with a small section that is only two lanes. Obviously there will be massive backups ahead of the two lane section. Expanding that section to match the rest of the road will clear the backups.

Depending on where the road is and how it fits into the rest of the network, there may only be six lanes worth of traffic and the congestion may be permanently cleared. On the other hand, the fact that the whole road can now actually take the six lanes of traffic may induce demand so that it will eventually fill up. But given that the road has already been built to six lanes almost everywhere, that’s not necessarily a bad thing: it means the investment isn’t totally wasted.

Now obviously my example is an extreme case, and I can’t say whether the low-capacity ramp under discussion is like my example. But it’s certainly possible. It doesn’t make sense to have one ramp in an interchange under capacity compared to the rest of the interchange and the amount of traffic using that ramp.

So overall I tend to be in favour of making interchanges and intersections match the capacity of the roads they connect, but opposed to adding lanes to the roads between the intersections. In many cases I would even rather match capacities by removing lanes from the roads between the interchanges.

My favourite example is at the corner of Erb and Caroline, where the single right turn from Caroline onto Erb frequently jams up. The obvious thing to do is to change that to a two lane right turn. On the other hand, the fact that it’s not catastrophically backed up proves that the Erb/Bridgeport combination really only needs one through lane in each direction, which suggests a rather severe road diet all the way across the city. So I’d be OK with reducing both roads to a combined total of a single through lane in each direction, plus turn lanes so that turning vehicles don’t hold up the through lane.