Results re. traffic volume and capacity

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To this point, we've discussed traffic capacity modeling and traffic volume data for the existing NM502 roadway. A simple model helps us to understand the effects of number of lanes, safety criteria, and speed on capacity. The simple model provides an approximate calculation of roadway capacity, in rough agreement with the capacity calculations of the NM502 Corridor Study. Traffic counting data has been compared with the models to determine present utilization. Utilization percentages vary somehwat, depending on what counting data and what capacity assumptions are made.

Both the Study and the simple model indicate that 4-lane Trinity is operating at 60-70% of capacity.

Both the Study and the simple model indicate that East Road is operating at 75-120% of capacity.

These assessments can be compared qualitatively with the on-the-road experience of driving in the two locations. Trinity (in my view) is a pleasant, usually open and free-flowing traffic pattern (ignoring the summer of 2011 construction mess at Diamond). East Road, during commuting peak, tends to be congested and significant queues and delays often occur.

Many complicated factors lead to fluctuations in traffic volume and driving conditions. A design goal of approximately 50% current utilization is required to cover fluctuations and growth in peak traffic levels, erratic driver behavior, and non-optimal driving conditions, e.g., accidents, emergencies, snow, or ice.

On the basis of these results, and given that cutting the number of thru-traffic lanes on Trinity from 4 to 2 would increase the utilization to over 100%, traffic utilization alone would suggest that the proposed reduction in number of through-traffic lanes on Trinity will increase congestion and seriously degrade its performance for transporting motor vehicles!

The Corridor Study argues that roundabouts will enable traffic at the intersections to travel so much more efficiently that there will be a net improvement in traffic flow over the entire corridor. In the next section, I will address this claim, and show that the opposite is true: the proposed roundabouts will further degrade traffic flow on the corridor.


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