Planned one-day closure - NCAR Mesa Lab - 10/10/15  more info>

Three-way stop on Mesa Road (follow-on)


Thanks for providing the rationale behind the three-way stop recently installed at the top of the Mesa Road, which we now learn came about as a result of a recommendation from a transportation engineer from Martin/Martin Engineering—an engineering consultant, not a decision taken by anyone at NCAR. The engineering consultant made the recommendation based on guidelines established in the Manual on Traffic Control Devices (MUTCD) developed by the Federal Highway Administration. For reasons involving "multiple users of the intersection, marked crossings through the intersection, potential for substantial conflicts between vehicles and pedestrians/bicyclists, the poor sight distance for vehicles approaching the intersection from the ramp looking to the left, and the need to transition from a long entryway roadway into a potentially congested and active parking area," the engineering consultant felt that "it was prudent to control the intersection with a multi-way stop control."

There is always a compromise between inconvenience/aggravation and possible safety issues. For example, sometimes people break the speed limit on the Mesa Road, and this could be cause for possible safety concerns. A way to control this would be to install speed bumps every few hundred feet on the road. Slower speeds would produce consequent safety benefits, but the aggravation/inconvenience factor would escalate, and this must be weighed against the relatively low risk of accidents involving automobiles, pedestrians, and cyclists based on a history of previous incidents.

A careful reading of the engineer's rationale leads me to believe that a prudent compromise between safety concerns of pedestrians, cyclists, and automobiles at the top of the hill would be a "yield to pedestrians in crosswalk" sign each way on the main Mesa Road, and a stop sign coming from the ramp down from the front door.

Again based on the "prudent" assessment of risk, weighing safety concerns against inconvenience/aggravation, I would note that the Mesa Road has been in operation for 45 years. Those 45 years have seen thousands of pedestrians, cyclists, and automobiles transit the intersection at the top of the hill. In those 45 years, how many accidents have occurred there?

Assessment of risk would indicate that the only new aspect of the intersection is the marked pedestrian crosswalks (paving the shoulders on either side of the hill only formalizes the use people have put to the sides of the road for decades). It's likely that 95% of the pedestrian traffic at that intersection consists of people transiting the intersection on the sidewalk from the parking lot to the hiking trail and back. Thus, the risk is higher for people crossing in front of vehicles using the ramp to the front door, reasonably warranting a stop sign there. For the other 5% of occasional pedestrian traffic who would use the pedestrian crossing from the hill road path to the ramp lane, a prudent assessment of risk would seem to indicate a "yield to pedestrians in crosswalk" sign for automobile traffic on the main Mesa Road. Could we agree that this compromise is reasonable, and install new signs accordingly?

Answered on May 19, 2011


After further consultation with SaSS and F&A, FM&S will leave in place the physical improvements designed by the professional licensed traffic engineer and engineering services firm. The design and construction of this intersection was part of the overall engineered plan for the entire road and parking lot replacement effort. If this employee wishes to bring this matter to the President’s Council and challenge the Council’s previous approval and decision, that remedy remains open to him/her.

Matt McMullen
Director, Facilites Management & Sustainability