Note. Like the blog said, these are my own thoughts and don't represent any governmental organizations with which I am affiliated. Note that Council has approved this project.
The New Mexico DOT representative gave an update on the 4th St. roundabout,which is at the 90% design, last Thursday at the T board meeting. Unfortunately, it was all about land acquisition and nothing about design or comparative costs to other treatments. William Mead, however, handed out what I think is the latest design and he and Joel Williams critiqued it as well as asking about costs. Here are some further, general thoughts.
First of all, I am neither pro nor anti roundabout. These are not instruments of the devil, but engineering designs meant to solve traffic problems. Whether they do is the big question. Whether a roundabout works well or poorly in a location depends on situation-specific design and traffic patterns. Several have pointed out that there are asymmetries in both the design of the proposed 4th Street roundabout, and that heavy traffic moves primarily east-west on 502 during "rush hour" in the a.m. and p.m. These are very peaky and short lived surges, as Mr. Mead showed, and would be the real test of whether the design would ease or cork heavy traffic. The rest of the day, Trinity Drive, like our massively overbuilt Diamond Drive, is quite underutilized. The question of whether the roundabout would work well during rush hour is best left to competent engineering analysis (note that the March 5, 2015 – 90% design T Board presentation by NMDOT/Souder, Miller & Associates on pg. 26 of the Agenda packet indicates an acceptable peak level of service). That said, I think building roads to provide high level of service at peak load, when peak load occurs over such a short time interval, is a massive waste of public funds. This ain't the Long Island Expressway we are talking about.
As far as an engineering analysis of the proposed roundabout, I am told the current firm is a good one. Recall that in the case of the first analysis of the multiple Trinity Drive roundabouts, the local critics nailed it and the County's consultants blew it, as was demonstrated when we finally brought in a well respected Midwestern engineering firm to re-run the numbers. We should never disparage our local brain trusts as being able to do these numerical analyses. Its not rocket science, and bomb scientists seem to be able to run the numbers quite well.
Deflection angles and other design geometries in roundabouts are critical. For example, the design that Mr. Mead showed had a lot of deflection for westbound 502 and far less for eastbound 502 One can surmise that this will result in higher eastbound and lower westbound speeds entering the roundabout. Has this been considered? The Diamond roundabout has very little deflection for Diamond Drive traffic headed for North and Barranca Mesas, as others have mentioned, with resulting high speed traffic from Diamond slowing at the last minute, if at all.
Safety is a concern. Multi-lane roundabouts are more challenging than single lane roundabouts to bicyclists and motorcyclists because of the chance the small vehicle will be overlooked and cut off during lane changes where the two wheeler is in a motorist's blind spot. Multilane roundabouts are a challenge for pedestrians and I think there are ADA compliance issues. We hear that low speeds in roundabouts cause fender benders rather than high speed intersection crashes. But a low speed crash to someone on two wheels is nothing to sneeze at. Bicyclists don't have air bags or crumple zones.Having once hit Mr. Pavement with a shoulder at low speed, I sported a brace to let an A/C separation heal.
Finally, cost. We did not get a cost comparison between total costs for a roundabout design versus using a traditional street layout. Costs for a roundabout will include demolition (including our little triangle park), land acquisition, and construction. Add to that delays due to construction. No numbers were forthcoming.
Whether we build a roundabout or a signalized intersection is a decision that should be (or presumably, was) made on the basis of all of the above considerations and a cost benefit analysis of competing designs. Politics and preferences will obviously be included in the mix.
But the bottom line is Los Alamos, even at peak load, doesn't have a traffic problem. We will never make the Texas Transportation Institute's Top Ten of time lost to congestion. Furthermore, a lot of talk of traffic growth projections are fairy tales that keep engineering and construction firms employed on the public dole. Traffic growth needs to be calculated on the basis of real estimates of local population and economic growth coupled to single occupant vehicle growth (vehicle counts). I've not seen any local ones that are credible. Indeed, some East Coast cities have been tearing down expensive 1960's vintage transportation projects designed for growth that never happened.
Meanwhile, Trinity Drive is still for the most part a stroad designed to get commuters back and forth to the Laboratory. Recent commercial and residential developments to the south of Trinity (and any that might materialize in the future) have to cope with crossing a street that is not designed to be an urban mixed use arterial, and whether or not we put in a roundabout, the rest of the vexing problems will remain. So much for a comprehensive plan.
Whether we really should spend tax dollars, even if it is other people's tax dollars, on a roundabout (or any other public works project) is a good question. What is the cost-benefit? Is it worth the price? What is the economic benefit? In this case, is it just a pretty entrance to town, followed by the depressing empty lots of our underutilized business district? What does it fix that is broken? The DOT representative correctly pointed out that these are mostly Federal dollars. But Uncle Sam is constantly borrowing to make ends meet. Perhaps like the late Nancy Reagan said, we should "just say no" to some projects and set an example of fiscal frugality for a change? Let's see some true critical analysis of this project, in the context of what we need to do to make this a Strong Town.