Albuquerque, NM – WHPacific, Inc. (WHPacific), the lead consultant firm for the project, worked in conjunction with the NMDOT’s: South Region Design, District 1, and Environmental Department to complete the I-25 Business Loop Phase I-A/B Alignment Study. WHPacific was responsible for leading the efforts to evaluate the existing conditions, develop alternatives for the corridor and intersections, and develop the study. In addition, WHPacific coordinated stakeholder coordination and public involvement meetings with the community and business owners; and provided the field survey and control, roadway concept layouts, and drainage evaluation and conceptual layouts. Once constructed, the double roundabout at New School Road and Smith Street will be the first 2-lane roundabout in New Mexico.
Project Uniqueness: The project is unique in that there are three roundabouts in succession on a major NMDOT roadway (I-25 Business Loop is a principle arterial) through a community with two of the southern roundabouts effectively working as a single intersection. This location will provide the first 2-lane double roundabout in New Mexico. The two intersections at New School Road and Smith Avenue are within only 400 feet of each other. The third roundabout is located to the north at NM 181 and the implementation of three roundabouts in succession will control the traveling speeds to approximately 25 mph to 30 mph. Safety Concerns: The Truth or Consequences School Superintendent demonstrated concern that the high school students would need to cross Date Street to interact with the elementary students located on the east side of Date Street, which would require the children to cross a four-lane roadway with assistance from a school official to stop traffic. This safety concern became the backbone for developing an alternative that would address the pedestrian safety and accessibility. The construction of the roundabouts will allow the students to safely cross only two travel lanes at a time and required to only look in one direction at a time. The slower traveling speeds (15 mph to 25 mph) will provide adequate time and distance for drivers to decelerate for pedestrians.
Value to the Public: The future value to the engineering profession includes setting a standard for reviewing and implementing unconventional alternatives through the public that might not be perceived positively at first. Initially, the community was unsure of the roundabout concept because it did not seem to allow for larger semi-truck vehicles or motorhomes with trailers. The community was also concerned about the businesses being affected by the installation of the roundabouts. However, during the second public meeting, those concerns were addressed with 3-D models depicting how larger vehicles interact with and traverse through the three roundabouts. These models had a positive effect on the community’s view of the roundabouts. The many benefits and safety aspects, especially reiterating the lower crash incidences and severity, were bolstered by figures and values from around the country and with roundabouts in New Mexico. The added benefits of providing safe pedestrian access and crossing the 4- lane Date Street roadway was discussed with the community as well.
Social and Economic Considerations: The community could see immediate added social benefits by adding a gateway feature to welcome tourists as they approach the NM 181 intersection while visiting Truth or Consequences and/or Elephant Butte and the Spaceport. A ‘sense of place’ will create an enhanced driving experience for driver, bicyclist, or pedestrian. Due to the nearby attractions, tourists and pass-through traffic travel often through the corridor. By forcing reduced travel speeds drives will be encouraged to take notice of the local businesses and restaurants thereby boosting the local economy. The sustainable design considerations include reduction of air emissions and reduced vehicle queuing in comparison to a traffic signal. In addition, the roundabout’s inner circle will provide an opportunity for water harvesting from storm runoff, which would reduce the overall water requirements needed to sustain landscaping and beautification.
Project Complexity Is No Problem: The three intersections at NM 181, New School Road, and Smith Avenue are in close proximity to each other and need to work in concert to create an efficient transportation system. The geometry for each of the roundabouts was designed to control the speeds of the traveling vehicles at the approach, through the roundabout, and at the departure. All conflicting movements are required to be within the range of 6 mph to 12 mph to ensure a balanced design. The roundabout at NM 181 was designed with the proper roundabout geometry and outside curvature to control the fastest path speed. The analysis was completed in accordance with the AASHTO Roundabout Design Guide methods.
Fulfillment of Client Needs: The roundabout alternatives at New School Road and Smith Avenue were evaluated in the study at the request of The NMDOT District and South Region Design Project Development Engineer. The project fulfilled all of the client’s expectations and needs in terms of properly evaluating the roundabouts for feasibility, satisfying the purpose and need and meeting the project budget and schedule for delivery. The project was developed using the NMDOT Location Study Procedures and an evaluation matrix was produced to determine the most feasible alternative for each intersection along the corridor. The matrix provided a method for weighing the benefits and downfalls of each alternative and placing a value on each criteria evaluated.
Costs: The estimated construction costs for the preferred alternative for NM 181 is $3,000,000 and for New School Road and Smith Avenue is $3,620,000, respectively.