The plans for New Mexico’s first diverging diamond interchange which features criss-crossing roadways and the addition of traffic lights on either side of the N.M. 14 that runs under Interstate 25. Courtesy image
The state Department of Transportation is about to start work on a major overhaul of the Interstate 25 interchange with N.M. 14 and Cerrillos Road south of Santa Fe, a project that looks perplexing on paper but which officials and engineers say is designed to improve safety and reduce traffic congestion.
Preparation for construction of New Mexico’s first “diverging diamond interchange,” which features criss-crossing roadways and the addition of traffic lights on either side of the state highway that runs under the interstate, is set to start next week. The department said in a news release that the work isn’t likely to be completed until the winter of 2016.
A combination of state and federal funds are being used to pay for the nearly $20 million project.
Rosanne Rodriguez, a spokeswoman with the transportation agency, said the bridges that carry traffic on the current network of ramps and overpasses are nearing the end of their design life. So the state hired the Albuquerque-based engineering and architecture firm Molzen Corbin to analyze the interchange and determine the best options moving forward.
Jerry Paz, a vice president at Molzen Corbin with three decades of experience as an engineer, said his group considered a number of possible solutions, including simply rehabilitating the current roadways. Paz said three years ago, his team and the state Transportation Department initially were skeptical when the Federal Highway Administration suggested the “diverging diamond” design as an option.
After running traffic simulations and weighing cost considerations, he said, his group settled on the odd-looking design. After a trip to Utah, where there are four such interchanges, state officials were on board, too. “We didn’t want to jump into it too early,” Corbin said. “But that [trip] confirmed in everyone’s mind that this was a good idea.”
Cities nationwide, including Springfield, Mo., and Brighton, N.Y., have started to adopt the model, which first appeared in Europe. The U.S. Federal Highway Administration has lauded the snaking design, saying this type of interchange allows traffic to move quickly while reducing the threat and severity of collisions.
The existing interchange is last point of access to I-25 for motorists leaving city limits on Cerrillos Road. Those seeking to get on northbound I-25 must cross two lanes of traffic on N.M. 14 to get reach an on-ramp. Likewise, motorists headed toward the city on N.M. 14 must cross two lanes of traffic if they want get onto southbound I-25.
But the diverging diamond interchange is aimed to solve that traffic conflict.
The plan calls for northbound and southbound lanes of N.M. 14 to diverge from their normal parallel structure and intersect at two points with traffic signals on either side of the I-25 underpass, creating a loose diamond shape. As a result, motorists who just want to stay on N.M. 14 will have to go through two sets of traffic lights.
Cerrillos Road and N.M. 14 will be expanded to three lanes in the immediate area of the interchange. Southbound travelers on N.M. 14 who want to get onto southbound I-25 will still be able to veer right onto an on-ramp. Likewise, northbound travelers on N.M. 14 who want to get onto northbound I-25 will still be able to veer right to an on-ramp.
However, those wishing to travel in the opposite direction on the interstate compared to their current direction on N.M. 14 will have to pass through a signaled intersection before reaching an on-ramp. While these motorists might have to stop at an intersection, they won’t have to turn in front of oncoming traffic, thus reducing the chance of a collision.
Paz said most collisions around the interchange actually have occurred on the northbound I-25 on-ramp from N.M. 14 and the I-25 off-ramp onto N.M. 14. The new design, he said, will provide longer merging lanes for getting on and off the interstate.
The plan also calls for the removal of three bridges associated with the northbound off-ramp from I-25 onto Cerrillos Road. Their absence means the state can save $10 million that would have been spent restoring those bridges. The main bridges carrying interstate traffic through the interchange will be renovated.
The project also calls for the construction of a trail in the place of the razed bridges that will tie into the Arroyo Chamiso Trail. That will allow hikers, bicyclists and other pedestrians the option of avoiding the interchange. Paz said the project also calls for wider shoulders for bicyclists who want to ride along N.M. 14.
Paz he is aware that some members of the public may be wary of the changes, but he said that as construction gets underway, the state will mount an outreach campaign that will include posting information about the project on a website. The goal, he said, is to give the public a reason to feel comfortable about the new interchange. And he’s confident that motorists will be fine with the design once they try it.
“It looks confusing on paper,” Paz acknowledged. “But as you drive through it, it’s not confusing at all.”
I-25 interchange project
Cost: $20 million, a combination of state and federal funds
Features:
• Longer merging lanes for getting on and off the interstate.
• Criss-crossing roadways and the addition of traffic lights on either side of N.M. 14 that runs under the interstate.
• Construction of a trail in the place of the razed bridges that will tie into the Arroyo Chamiso Trail.
How it works:
• Motorists who just want to continue on N.M. 14 will go through two sets of traffic lights.
• Southbound travelers on N.M. 14 who want to get onto southbound I-25 will still veer right onto an on-ramp; northbound travelers on N.M. 14 who want to get onto northbound I-25 will still veer right to an on-ramp.
• Northbound drivers on N.M. 14 aiming to travel south the interstate and southbound drivers aiming to travel north on the interstate will have to pass through a signaled intersection before reaching an on-ramp, reducing the chance of a collision.
By: Chris Quintana (Santa Fe New Mexican)
Click here to view source article.
I-25 interchange project
Cost: $20 million, a combination of state and federal funds
Features:
• Longer merging lanes for getting on and off the interstate.
• Criss-crossing roadways and the addition of traffic lights on either side of N.M. 14 that runs under the interstate.
• Construction of a trail in the place of the razed bridges that will tie into the Arroyo Chamiso Trail.
How it works:
• Motorists who just want to continue on N.M. 14 will go through two sets of traffic lights.
• Southbound travelers on N.M. 14 who want to get onto southbound I-25 will still veer right onto an on-ramp; northbound travelers on N.M. 14 who want to get onto northbound I-25 will still veer right to an on-ramp.
• Northbound drivers on N.M. 14 aiming to travel south the interstate and southbound drivers aiming to travel north on the interstate will have to pass through a signaled intersection before reaching an on-ramp, reducing the chance of a collision.
By: Chris Quintana (Santa Fe New Mexican)
Click here to view source article.
