By WILLIAM C. MEAD

Round and round we go?

Would you consent to costly, painful surgery that might or might not improve your health and could result in increased blockage of one of your major arteries?

The wheels of transportation progress have turned and we’re now faced with the prospect of having our very own two-lane roundabout (RDB) built on Trinity Drive (N.M. 502) at Central Avenue, beginning in the Spring of 2017.

Over the past 20 years or so, roundabout proponents have generated three large proposals. The most recent grand plan, in 2011, proposed reducing Trinity to two lanes and installing nine roundabouts. A $300,000 transportation study was performed by MIG, Inc., a roundabout engineering firm. After review of the study by several concerned county residents, the County Council obtained a second professional opinion that confirmed the citizens’ review: the proposed scheme would not operate as claimed by MIG, but would create a traffic nightmare. (More historical and technical details are available at www.wcmead.org.)

In the 2011-2012 discussions, eight roundabouts died, but one survived, namely the RDB currently planned for Trinity at Central. Conceptually, that RDB appeared to be satisfactory, so that plan has moved forward. Recently, the nearly final design has been completed and, alas, the detailed plans differ significantly from the conceptual design.

Unless there is a decisive intervention, the RDB at Trinity and Central will be built. If so, I think the following are highly predictable outcomes. Millions of dollars will be spent, some land will change hands, a lot of existing pavement will be removed and even more new pavement will be installed. Existing landscaping at the current Central-Trinity intersection will be destroyed, and a 60’ circle at the central island of the RDB will be landscaped. There will be a year or so of complete chaos during construction followed by a period of mutual adjustment (1-2 years) of drivers and the roundabout itself.

Now, predictions become less certain. Two-lane roundabout installations around the country have had widely varying amounts of success.

Here are three scenarios:

• In the worst cases, the RDB fails to deliver satisfactory performance. In these cases,  within 3-5 years, millions more are spent re-redesigning and re-rebuilding the intersection. I think there is about 30% chance that the planned Central/Trinity RDB will fall into this category. Known issues might lead to unacceptably high accident rates, severe traffic snarls at peak hours, or even business failures in the area.

• In middle-of-the-road cases (50 percent probability for this RDB), a large portion of the users adapt to the RDB and the changes are accepted by the community as a whole. Some of these roundabouts can still be notorious traffic hazards. I predict, for example, that the N.M. 502 RDB will be avoided by pedestrians and used very little by bicyclists. Among drivers, some will seek alternate routes. Diverting commuters from N.M. 502 to the truck route is a goal among RDB advocates, and I think this will happen to the extent that the Truck Route can absorb extra traffic, to the detriment of Los Alamos businesses. I think it likely that, over the first five years, we will see an accident rate that will put this intersection among the top three in the county, probably at the top position. Visitors to Los Alamos will find the RDB confusing.

• In the best cases, the roundabout becomes a classic success story. The users find the roundabout efficient and convenient. I’d predict about a 20 percent chance of achieving Roundabout Valhalla in this project.

The total project cost for the N.M. 502 corridor revisions from Knecht Street to Tewa Loop is now placed at $8 million, about twice the 2012 estimate. Speaking of costs, in all my research and questioning, I have yet to find clear answers to the questions of how much does a roundabout cost, and how does the cost compare with that of “smart signals” (about $300,000, excluding pavement changes). Maintenance costs are likewise hard to obtain. Such information seems to be buried in places only an auditor could love.

In summary, I think the N.M. 502 roundabout plan is unwise and that the cost to benefit will be unfavorable compared with the much simpler alternative of adding a signal and making necessary lane modifications on Trinity near Central (the approach first chosen in 2007!).

N.M. 502 is obviously a major artery for Los Alamos residents and businesses. Should we continue with the planned surgery?