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ADOT seeks improvements to SR 189 as Mariposa Port expansion nears completion

Nogales highway is vital link to international trade with Mexico
October 10, 2013

PHOENIX — At less than four miles long, State Route 189 in Nogales is one of the shortest routes on the state’s highway system, but it is one of the most critical when it comes to commerce and trade due to its close proximity to the U.S.-Mexico border.

The highway serves as a bypass route for commercial truck traffic to and from Mexico. Much of the produce that comes through Nogales ends up making its way throughout Arizona and the rest of the country. It’s an essential corridor and it’s only going to get busier, according to the Arizona Department of Transportation.

Traffic volumes are expected to spike in the future, now that the Mariposa Port of Entry, one of the busiest cargo ports along the U.S.-Mexico border, is nearing the completion of a four-year, $225 million reconstruction and modernization project in 2014. For instance, the port of entry currently processes between 1,200 and 2,400 trucks per day and this number is expected to climb to 3,000 trucks by 2014.

With additional traffic on a roadway that is already congested, ADOT is exploring options for a new or expanded highway to handle the increased volume of traffic.

Beginning in early 2011, shortly after the federal government accelerated the Mariposa Port of Entry project after receiving American Recovery and Recovery Act funds, ADOT began evaluating long-term improvements to the SR 189 (locally known as Mariposa Road) corridor.  

ADOT, along with the Federal Highway Administration, launched an engineering and environmental study for the SR 189 corridor. The goal of the study was to evaluate alternatives to handle the projected increased volume of traffic and relieve congestion on SR 189. Initial estimates range from $50 to $215 million to complete the improvements.

While no funding has been identified to pay for any of the long-term improvements at this time, ADOT understands the improvements are critical to Nogales and the trade industry, and is looking into potential funding sources, which may include local, state, federal and Public-Private Partnerships (P3).

The agency is moving forward with some interim improvements that will begin this fall. The work is expected to accommodate the additional truck traffic expected following the completion of the Mariposa Port of Entry.

This week, ADOT launched a $1.5 million project that includes signal timing synchronization at the Interstate 19 interchange and throughout the entire SR 189 corridor. The upgraded traffic signal system, which uses a microwave technology to interconnect to the traffic signal controllers, will share traffic data in real time. The signals will continuously adapt to traffic demands, thus reducing congestion and travel times along the corridor.

Additional enhancements include the construction of dual eastbound left-turn lanes at the SR 189 to northbound I-19 entrance ramp intersection and widening the northbound I-19 entrance ramp on the departure side of the intersection. The work is expected to be completed by the end of the year.

For more information on the State Route 189 Study (International Border to Grand Avenue), please visit

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