Glenwood bridge detour numbers show 22 percent drop in traffic; delays remain

An overall 22 percent reduction in average daily vehicle trips through Glenwood Springs during the Grand Avenue Bridge closure and detour is an impressive accomplishment that’s worth celebrating, bridge project officials said.

But they’re also quick to acknowledge that the reduction has done little to keep travel delays to a minimum at peak hours, when it can take upward of two hours just to get through town during the weekday afternoon and evening commuter rush.

The reduction is little consolation to the people trying to get to and from upvalley jobs and homes west of Glenwood Springs who say they can’t take the bus, or for local residents who are dealing with traffic spilling onto side streets every day. The effect also fulfills the expectation of an independent review that found a 35 percent cut in traffic would be needed to prevent major delays.

The Colorado Department of Transportation marked the midway point of the 95-day detour period this week, as crews prepare for a major concrete pour tonight and Saturday morning on the bridge deck and southernmost span that will land in downtown Glenwood Springs.

It’s a critical step toward completion of the final segment of the new, $126 million bridge, and in keeping the project on schedule.

CDOT has also released data from traffic counts taken along the Grand Avenue, Eighth Street and Midland Avenue detour route during a four-day period in mid-September after area schools had started back up for the school year.

While traffic volumes since the detour went into effect in mid-August have not come close to the targeted 35 percent reduction, enough people are taking the bus or finding alternative ways to get around to make some difference, said Graham Riddile, project engineer for CDOT.

“We are seeing a lot of positive behavior to try to help the situation, and we would like to see more. That would be great,” Riddile said.

One concern, he said, is that as the weather gets “colder, wetter and darker” in the coming weeks, people will begin to fall back on old routines.

“We encourage people to stay on their good habits, and to keep doing what they’ve been doing,” he said. “If that starts changing, that’s when we’re going to see these numbers going back up.”

peaks and plateaus

The traffic counts confirm a definite “peak to plateau” pattern during the heaviest morning and evening periods, Riddile said.

Overall there’s been a reduction of about 7,300 vehicle trips, on average, from a pre-detour estimate of 32,560 trips to an actual number of 25,277 trips going both directions through town per day, for a 22 percent reduction.

But the peak morning and evening travel demands are far different, the traffic counts revealed.

The morning rush recorded 4,500 fewer trips going south through Glenwood Springs than estimated based on pre-detour statistics, for a 26 percent reduction in traffic.

Morning traffic also exceeds the detour capacity for a shorter span of time, for about an hour around 6 a.m. based on the Sept. 11 to 14 counts.

The afternoon/evening period, when traffic is coming back through town headed north, saw only 2,800 fewer trips compared with the pre-detour estimate during that four-day stretch, for an 18 percent reduction.

That explains the large difference in traffic patterns from morning to afternoon, and the heavier congestion well into the evening on given days, Riddile said.

The afternoon traffic typically begins to back up around 2 p.m. and lasts much longer, until 7 p.m. or later.

NOT COUNTING FRIDAY

The average counts did not include a Friday, which has proven to be the worst day of the week for mid- and late-day traffic.

“Taking a look at these numbers, it’s clear we are hitting our capacity earlier and for a longer period of time in the afternoon,” Riddile said.

Reducing detour traffic to a more manageable level, especially during those peak times, was a primary goal for project officials.

Before the detour, peak traffic reached 1,800 vehicles per hour in the afternoon, and nearly that same number in the morning.

What had been six traffic lanes on Grand Avenue and Midland Avenue through town and over the Colorado River before the detour was cut to just two lanes for the better part of the detour route, Riddile noted.

To make the detour flow more smoothly, traffic managers figured there would need to be a reduction of about 700 vehicles per hour.

As things have played out, the detour capacity is indeed around 1,100 vehicles per hour. At that volume, the long delays and traffic behaviors being observed are exactly what was predicted going in, Riddile said.

“We knew it was a matter of getting traffic down to that capacity, or as close as we possibly could, to minimize that queuing effect we see,” he said.

When the detour does hit capacity and backups begin, that’s when traffic starts to cascade onto side streets such as Blake and Midland, and even onto County Road 154 at Buffalo Valley to South Grand.

ONGOING angst

Meanwhile, the traffic frustrations play out daily in comments on the Roaring Fork Road and Weather Facebook page and other venues, at times reaching the boiling point.

“I’m thinking this morning how the elite in the world don’t seem to have any conception of what the average person goes through day in and day out just trying to provide for their family, and to get to and from work,” one recent commenter lamented.

“And that makes me angry, especially in this case, where CDOT and other planners did not adequately plan for traffic delays and routing in Glenwood,” she said, touching off a long thread of responses.

“The real problem isn’t even traffic,” another person wrote in response. “It’s that Aspen needs to seriously start providing some affordable housing to their own workforce.”