The Florida Department of Transportation (FDOT) has prepared this Interchange Operational Analysis Report (IOAR) for the SR-93/I-75 east side ramp improvements at Griffin Road. The interchange of I-75 at Griffin Road is located in western Broward County within the Town of Davie, and near the City of Weston and Town of Southwest Ranches.
A Systems Interchange Modification Report (SIMR) was approved by the FDOT and the Federal Highway Administration in 2011, as part of the SR 93/I-75 PD&E Study (FM#419343-1-22-01). Improvements were approved for the I-75 corridor including express lanes and multiple interchange improvements, including improvements at the Griffin Road interchange. This report supports an ongoing design project (FM #432709-1) to implement previously approved interchange safety and operational improvements.
Enhancements to the northbound I-75 on and off ramp termini are intended to enhance safety, and add capacity and vehicular storage for the eastbound left turn movement on to the northbound I-75 on-ramp, and for the northbound I-75 off-ramp right-turn movement onto eastbound Griffin Road. The eastbound Griffin Road left-turn movement to the northbound on-ramp currently experiences excessive delays and queuing during the morning peak hours of operation. The northbound I-75 off-ramp free-flow movement merge onto Griffin Road is beginning to experience difficulty merging on to Griffin Road in peak hours. These conditions are expected to deteriorate with future anticipated traffic growth.
The proposed interchange improvements, as part of the design project, include reconstructing and signalizing the I-75 northbound to eastbound off ramp, northbound to westbound off ramp, and westbound to northbound on ramp, and adding turn lanes for the new signalized movements. The improvements were evaluated assuming an opening year of 2020 with a design year of 2040.
The purpose of the IOAR is to document the need for the interchange improvements, and evaluate the expected traffic operations and safety benefits and impacts from the east side interchange improvements. The traffic operations of the I-75 northbound off-ramp termini intersection with and without the proposed improvements were analyzed. The analysis follows the methodology described in the I-75 at Griffin Road IOAR Methodology Letter of Understanding (MLOU).
Results from the analysis indicate that the new signalized intersection will operate at an acceptable LOS D in both peak hours in 2020. By 2040 the overall intersection will operate at overall LOS E in the AM peak hour and LOS D in the PM peak hour. Compared with the No Build condition, the eastbound left turn movement delay is significantly reduced from over 370 seconds in the AM peak hour and 84 seconds in the PM, to 72 seconds in the AM and 70 seconds in the PM. In addition, the eastbound left turn queue length is reduced from 1,190 feet in 2020 to 493 feet, and from 1,711 feet to 623 feet in 2040.
Purpose and Need
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The purpose of the proposed interchange improvements at the east side of I-75 and Griffin Road is to provide increased capacity, improve connectivity between facilities, and enhance safety conditions at the interchange. These improvements will meet the long term transportation needs at the interchange (through year 2040) and support anticipated population/employment growth and economic development within the region. Enhancements to the northbound on and off ramp termini are intended to enhance safety, and add capacity and vehicular storage for the eastbound left turn movement and northbound right-turn movement.
This will mitigate existing and future operational deficiencies. The eastbound to northbound left-turn movement currently experiences excessive delays and queuing during the morning peak hours of operation. Those delays and queues are expected to increase by 2020 and 2040. In addition, the northbound to eastbound right turning vehicles have a short merge distance (350 feet) onto Griffin Road prior to reaching the Griffin Road and SW 148th Avenue intersection. With the anticipated increase in future traffic volumes, the merge condition is expected to worsen.
It is important to bring the free flow on and off ramp movements under signal control to provide safe gaps in eastbound and westbound Griffin Road traffic for the northbound to eastbound, and eastbound to northbound turning movements. A longer distance between the northbound off ramp and the SW 148th Avenue intersection will better accommodate eastbound queues on Griffin Road at SW 148th Avenue.