Traffic engineers in LR, NLR plan for bridge closure

Signal technician Jacob Mahan with the North Little Rock Traffic Department demonstrates the traffic cameras, including one showing the Main Street Bridge, that will be used to manage traffic • ow during the construction of a new Broadway Bridge.
Signal technician Jacob Mahan with the North Little Rock Traffic Department demonstrates the traffic cameras, including one showing the Main Street Bridge, that will be used to manage traffic • ow during the construction of a new Broadway Bridge.

As many as half of the 24,000 vehicles now using the Broadway Bridge daily are projected to use the nearby Main Street Bridge as an alternative when the Arkansas River crossing is closed for up to two years while a new one is built.

The traffic modeling forecast developed by Metroplan, the long-range transportation planning agency for central Arkansas, predicts that as much as 30 percent of the Broadway Bridge traffic will migrate to the Interstate 30 river bridge, which already carries more than 100,000 vehicles daily and is scheduled to be widened or replaced with a larger structure after the new Broadway Bridge is built.

The remaining vehicles will use either Interstate 440 and Interstate 430 bridges or -- in the case of 5 percent to 15 percent of the traffic now on the Broadway Bridge -- avoid crossing the river between Little Rock and North Little Rock altogether, according to Metroplan's model.

Casey Covington, a transportation planner for Metroplan, said no other tool exists to forecast what might happen when the bridge is closed to traffic.

The traffic modeling "attempts to predict future travel behavior based upon past behavior and is the best tool we have, but is only an educated guess," he said.

Still, the Broadway Bridge traffic that is forecast to use the Main Street Bridge will almost double the volume that is on that bridge now. Planning to deal with that eventuality has kept traffic engineers on both sides of the river busy.

Last week, the North Little Rock Traffic Division gave briefings to City Council members on its preparations to address traffic concerns associated with the impending closure of the Broadway Bridge.

Chris Wilbourn, the division's director, told council members that the "latest best guess" from state highway officials is that the Broadway Bridge will be closed to traffic in April.

In the meantime, the division has been purchasing cameras, computers, servers and large monitors in a bid to be able to view and react to traffic conditions in real time, he said.

"Knowing what's [happening] downtown in our city is the priority," Wilbourn said.

The cameras, which will be able to pan and zoom, will be set up at key locations around downtown, as well as locations leading into the city, and will augment police cameras already set up, Wilbourn said. The new equipment also will allow agency staff to monitor traffic from the cameras already in place on the Little Rock side and, significantly, allow staff to change the timing of the traffic signals as conditions warrant, he said.

Much of the traffic that now goes onto the Broadway Bridge in the morning travels south from Pike Avenue and from John F. Kennedy Boulevard and Main Street in North Little Rock, especially if motorists want to go west of downtown, such as to the state Capitol. Other traffic comes from North Hills Boulevard to the east.

Wilbourn is considering another change that will have to be approved by state highway officials; Garver LLC, the engineering firm designing the bridge; and the contractor.

Plans now call for traffic from Pike Avenue to continue east on West Broadway past the Broadway Bridge to the Main Street Bridge. Wilbourn said he believes it might be better to direct that traffic onto Riverfront Drive and east to the Main Street Bridge because traffic on West Broadway turning right onto Maple Street to the Main Street Bridge will be slowed by eastbound traffic wanting to turn left onto Maple.

Funneling the traffic from Pike to Riverfront will eliminate that conflict, he said.

The Arkansas Highway Commission is scheduled to open bids Sept. 17 on the project to replace the 91-year-old bridge, which state highway officials said is becoming increasingly expensive to maintain.

The Arkansas Highway and Transportation Department made an initial commitment of $45 million for the bridge replacement, but the latest estimates, as a result of preliminary engineering studies, have increased the amount to $58 million. Pulaski County has committed an additional $20 million to the project to cover the additional cost of the design that local officials preferred -- a twin basket handle arch bridge.

The new bridge will have four 11-foot-wide travel lanes with 4-foot shoulders and a 16-foot shared-use path on the east side of the bridge.

But the planned bridge is more than two years from carrying traffic. Wilbourn and Little Rock traffic engineer Bill Henry are trying to anticipate the traffic headaches in the interim.

On the Little Rock side, Henry already has said the city will increase the cycle of its traffic signals from the Main Street Bridge to 90 seconds to "push through" the higher volume of traffic. The cycle now is 70 seconds.

The city also will extend two-way traffic on South Scott Street to East Sixth Street. The two-way portion of Scott now ends at East Capitol Avenue. Extending it to Sixth Street will allow traffic to go west on Sixth, which is one way and can carry a high volume of traffic west to the state Capitol.

For northbound traffic in the afternoon rush, Henry said a protected left-turn lane will be added for eastbound traffic on West Third Street at Scott to allow traffic to turn north toward the Main Street Bridge.

How well the modifications and traffic control work will determine what some motorists ultimately will do, Covington said.

"Modifications being made to the approaches to the Main Street Bridge -- signals -- will allow for an increase in traffic," he said. "The effectiveness of these changes will have a large effect on how many of the peak hour trips divert to Main Street versus I-30."

Still, whatever plans are made, Wilbourn told North Little Rock aldermen last week, the early days of the Broadway Bridge closure are "probably not going to be super pretty."

But motorists will adjust eventually, said Jim McKenzie, the executive director of Metroplan.

"It may take a few weeks, but [traffic] will seek an equilibrium," he said. "People thought the Interstate 430/Interstate 630 project would be a nightmare, but people adjusted.

"I think we are underestimating the intelligence of the folks who drive around here."

A section on 07/28/2014

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