Rebuttal to Arguments

Opponents of change to Iris speak to three primary concerns: Traffic congestion or slower travel, neighborhood cut-through traffic, and emergency access.

With 4:3 rebalancing, travel time increases a little

It seems logical that halving the number of through-lanes would double roadway congestion. But that is not what happens with 4 to 3 conversions. The center turn lane means traffic in the inner lanes is not held up by left-turning vehicles. A rebalanced road flows somewhat slower but much more steadily. Thus, the average time it takes to traverse the entire 3-lane segment of the corridor may be the same or less than it was before the rebalancing. That is how  the 3-laned Arapaho Avenue is able to handle as many trips per day as Iris Avenue now can with its 4 lanes.

Thus far, the City’s documents briefly address traffic congestion. They state that today it normally takes four or five minutes to drive from 28th to Broadway. For Alternatives A and B, they used a minus or negative symbol to acknowledge that the three-lane configuration would increase the drive time. They do not present any numbers for that but say such information will come this summer after traffic modeling is complete.

Neighborhood streets cut-through traffic is preventable

Some people are reasonably concerned that the change in Iris Avenue’s configuration will cause some drivers to leave the corridor and try to accomplish this short journey by cutting through adjacent neighborhood streets. The City’s web page states, “…we heard from the community that it is important to maintain the character of the surrounding neighborhoods and on streets like Glenwood Drive, Grape Avenue, Kalmia Avenue, and others. The City of Boulder is evaluating improvements such as traffic calming on nearby streets as a concurrent project.” They do plan to address the issue.

Elsewhere in America, when cities have changed four-lane roads with Iris’ traffic volume into this three-lane configuration, travel has not significantly slowed and traffic congestion has not significantly increased. Therefore, drivers will have not much incentive to cut through neighborhoods. Nonetheless, those neighborhoods already see some people driving way too fast and the city should add a suite of traffic calming features to those streets. We need the traffic calming regardless of whether the speeding drivers are neighbors, visitors, service workers, or Iris avoiders. We ask the City to move forward with traffic calming in adjacent neighborhoods as part of the Iris Avenue project.

What About Folsom?

Some would have you believe that the 2015 rebalancing of Folsom is proof positive that road rebalancings are inevitably a disaster. For those who don’t know the history, here’s a recap. In 2015, Folsom was rebalanced between Valmont and Canyon. Drivers immediately observed an increase in congestion in the southbound lanes of Folsom at Spruce and Pearl. Unfortunately, City staff at the time had not warned the community or City Council that there might be some reductions in throughput, at least until signal timings could be adjusted to better flush the corridor. The uproar was enough to cause City Council to order that the rebalancing be reversed, well before City staff had an opportunity to evaluate or implement mitigating strategies. In fact, City staff did not even have an opportunity to quantify the delay associated with the rebalancing, which, by some accounts was a couple of minutes and, by others, much longer. Accordingly, this rebalancing has taken on mythical dimensions when it’s possible that  modest changes to signal timing would have substantially reduced the delay at Spruce and Pearl or have eliminated it altogether. We will never know for sure.

What we do know for sure is that the team working on Iris is almost completely different from the team that worked on Folsom, that the current process is much more transparent to the entire community, and that the bookends of Iris have been preserved to forestall any catastrophic impact on travel time.



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