Study Overview

• A high number of crashes within the interchange occur at four locations: 1). the southbound off-ramp/St. Michael’s Dr. intersection, 2). the southbound on-ramp to St. Francis Dr., 3). eastbound St. Michael’s Drive between the northbound off-ramp and Galisteo Street, and 4). the west to northbound on-ramp to St. Francis Dr. (view summary)
  
• Two additional hot spots were identified: 5). the stop-controlled intersection at the northbound off-ramp and St. Michael’s Dr. and 6). the northbound loop on-ramp to St. Francis Dr.
• A higher-than-expected crash frequency was identified at the four signalized cross street intersections adjacent to the interchange area.
• Three pedestrian crashes have occurred within the Study area. (view summary)
  

• Re-stripe Existing St. Francis Drive: The Re-Striping Alternative would return the travel lane configuration along St. Francis Drive, from Siringo Road to West San Mateo, to the four lane configuration that existed before 2005 (view map).This would efficiently address the prominent merge lane deficiency that currently exists at the three on-ramps entering St. Francis Dr.; however, many deficiencies (e.g. physical, operational, safety, and multimodal) would remain and the new lane drops on St. Francis Dr. could induce operational and safety concerns.
• Modern Roundabout: This alternative would replace the existing bridge and interchange with an at-grade modern roundabout (view map). Although it addresses project needs, the roundabout would pose multi-lane complexity and driver expectancy/familiarity concerns and result in operational deficiencies under 2035 conditions.
• Single Point Urban Interchange (SPUI): This alternative would convert the existing interchange into a SPUI, with all on and off-ramp connections on St. Michael’s consolidated into a single signalized intersection (view map). The SPUI would address the Study purpose and need but would have significant impacts to traffic during construction and a high cost relative to other alternatives.
• Diverging Diamond Interchange (DDI): This alternative would convert the existing interchange into a DDI, with mainline eastbound and westbound traffic on St. Michael’s Dr. “crossed over” to eliminate left turn phases at the signalized ramp intersections (view map). The DDI alternative would address purpose and need but would result in an anticipated increase in crashes, severe impacts to traffic during construction, higher costs, and additional right-of-way requirements along St. Michael’s Dr.

At the conclusion of Phase IA, The Study Team recommended that the following alternatives be advanced for more detailed evaluation in Phase IB (Phase IB Report PDF):

• No-Build: The No-Build Alternative provides a basis upon which each of the initial build alternatives for the proposed interchange improvement project can be compared. This alternative would have no project-related impacts but does not address any physical, operational bicycle/pedestrian, or safety related deficiencies.
  
• Signalized Intersection: This alternative would replace the existing bridge and interchange with a conventional at-grade intersection at St. Francis Dr. and St. Michael’s Dr. (view map). The Signalized Intersection Alternative addresses Study purpose and need and provides for an at-grade alternative for comparison with interchange alternatives.
• Diamond Interchange: This alternative would convert the existing half diamond interchange into a full diamond configuration maintaining the grade separation of St. Francis Dr. over St. Michael’s Dr. (view map). The Diamond Interchange addresses Study needs and provides a greater range of potential benefits compared to other alternatives.
• Ramp Reconfiguration: The Ramp Reconfiguration Alternative would improve the on- and off-ramps on the east side of the interchange, replacing the two existing northbound on-ramps with a single “trumpet” style ramp (view map). This alternative addresses Study needs and provides greater potential benefits compared to other alternatives.
• Split Bridge Northbound/Southbound Left-on Access: This alternative would convert the existing interchange into a split bridge configuration, with the St. Francis Dr. mainline split to cross over St. Michael’s Dr. on two new structures. On-ramps from St. Michael’s Dr. would access St. Francis Dr. on the left (view map). It addresses project needs but provides an inferior range of benefits compared to
  other alternatives.

In addition to these alternatives, the Phase IB Study included an alternative whereby St. Michael’s Dr. would be constructed as a four-lane roadway within the interchange, in recognition of on-going City of Santa Fe planning efforts to undertake a future road diet study on St. Michael’s Dr. (view image) Several minor intersection alternatives were also considered at Siringo Road/St. Francis Dr., West San Mateo Road/St. Francis Dr., and the southbound off-ramp intersection at St. Michael’s Dr.

Based upon the detailed evaluation, the Phase IB recommended alternative is the Ramp Reconfiguration with the four-lane option on St. Michael’s Drive and the Siringo Road/St. Francis Dr. intersection configured to include dual left-turn lanes from northbound St. Francis Dr. to westbound Siringo Road (view map).