Peer Review by Ourston Roundabout Engineering

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A peer review requested in early August by the Transportation Board was provided on August 30, 2011 by Ourston Roundabout Engineering. Ourston's review confirmed our important conclusion that the proposed single-lane roundabouts would not have enough capacity to handle existing peak traffic on NM502.

"Our analysis shows that single lane roundabouts will not adequately handle the
existing or future traffic volumes for select approaches."

Ourston agreed with some of our other criticisms of MIG's Study.

"Adding right hand turn lanes in the future condition is not a realistic way to add capacity."

"When V/C ratios exceed 0.85, queuing and delay estimations are highly variable and unpredictable. It is not recommended to design for V/C ratios exceeding 0.85."

Ourston also suggested that two-lane roundabouts could be appropriate for use on NM502. For several reasons, I consider that this would be unwise and would not meet Los Alamos County goals: two-lane roundabouts are yield-intensive and require quite a bit of real-time decision making (conditions difficult for non-aggressive drivers), two-lane roundabouts have many built-in traffic conflicts, and two-lane roundabouts present complications and hazards to pedestrians, bicyclists, and motorcyclists.

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