Executive Summary
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In August 2016, the Federal Highway Administration approved the Interchange Modification Report (IMR) prepared by the Florida Department of Transportation (FDOT) for the improvements at the I-10 interchange with SR 121, which can be found in Appendix A. Following the IMR approval, FDOT proposed signalizing the ramp terminal intersection of westbound I-10 with SR 121 as an immediate enhancement to improve existing operational and safety deficiencies of the subject intersection. This concept was documented in the approved September 2019 Interchange Operational Analysis Report (IOAR), which can be found in Appendix B. To reduce the construction costs associated with the August 2016 IMRapproved Build Alternative, FDOT proposed interim improvements that will provide significant operational and safety
improvements compared with the No-Build Alternative. An overview of the changes with the Interim Build Alternative are as follows:
- Add directional ramp for traffic from westbound I-10 to northbound SR 121
- Improve SR 121 in the northbound direction by widening the road to two lanes south of the SR 121 and George Hodges intersection
- Install a new traffic signal to control the northbound SR 121 and westbound I-10 off-ramp movements
This IMR documents the analysis findings of the Interim Build Alternative proposed at I-10 and SR 121 interchange.
The following deficiencies have been identified under the Existing Year (2020) conditions that are anticipated to improve
as part of this project.
- The I-10 and SR 121 interchange is a partial cloverleaf configuration with nonstandard loops in the southeast and northwest quadrants. Under existing conditions, these loop ramps that were built with lower design speeds, hinder normal traffic operations, especially in the westbound I-10 direction. The westbound I-10 off-ramp is currently a three center radii loop ramp that terminates at a stop-controlled intersection with SR 121. This configuration results in interrupted flow and traffic backups, specifically during the AM and PM peak hours.
- Southbound SR 121 commuters encounter poor sight distance due to the vertical curve over I-10. The I-10 westbound ramp terminal intersection is unsignalized. Hesitation to perform the turning movement to head north on SR 121 due to poor sight distance over the vertical curve leads to high delays for motorists exiting the freeway. Drivers of heavy trucks making this movement have been observed making risky decisions. These conditions result in unsafe travel conditions and an increase in queue length that backs into mainline I-10 impeding its operations.
- The study area possesses heavy truck traffic, which accounts for more than 17 percent of peak hour traffic volumes. The grade differentials and curves of the loop ramps paired with the high truck volumes generate speed differentials that deteriorates operating conditions and safety.
The deficiencies found in the Existing Year (2020) analysis are anticipated to worsen with increased traffic volumes by Design Year (2045), even with the westbound I-10 ramp terminal signalization. Without improvements to this interchange, the traffic operations and safety within the study area will continue to deteriorate, the queue lengths and delays will increase, and the number of crashes will rise.
This IMR compares the operational and safety performance of the No-Build Alternative, the No-Build with Signal
(IOAR Concept) Alternative, and the Interim Build Alternative.
Purpose and Need
Download the Purpose and Need (PDF, 202.4KB)
The purpose of this project is to provide interim capacity relief and improve traffic operations and safety near the SR 121 and I-10 interchange in Baker County.
The I-10 and SR 121 interchange is a partial cloverleaf configuration with loops in the southeast and northwest quadrants. Under existing conditions, these loop ramps hinder normal traffic operations, especially in the westbound I-10 direction. The westbound I-10 off-ramp is currently a three-center radii loop ramp that terminates at a stop-controlled intersection with SR 121. This configuration does not provide efficient operations and results in traffic backups, specifically during the AM and PM peak hours. Additionally, southbound drivers encounter poor sight distance due to the vertical curve over I-10.
In the year 2020, SR 121 carried an Annual Average Daily Traffic (AADT) of 12,100 vehicles to the south and 13,000 vehicles to the north of I-10 on a two-lane facility as shown from counts collected between January 14, 2020 and January 16, 2020. The I-10 mainline within the project study area carried an AADT of 33,100 vehicles to the west of SR 121 and 39,600 vehicles to the east of SR 121 on a four-lane facility from Existing Year (2020) traffic counts.
If no improvements are made, traffic operations and safety within the interchange area will continue to deteriorate as traffic and freight movement to and from the City of Macclenny increases. For this reason, the ultimate build improvements from the approved IMR (August 2016), which can be found in Appendix A, were proposed to address operational and safety deficiencies of the study area. For immediate relief, FDOT District Two proposed to install a signal at the ramp terminal intersection of the I-10 westbound off-ramp with SR 121 through a Traffic Operations Push Button Contract as documented in the approved Interchange Operational Analysis Report (September 2019) provided in Appendix B. With the continued growth in traffic volumes and even with signalization of this ramp terminal intersection, traffic operations will progressively worsen and deteriorates conditions at the I-10 and SR 121 interchange by Design Year (2045) if no geometric roadway improvements are made. Therefore, this report analyzes the improvements proposed with the Interim Build Alternative that includes adding a directional ramp to westbound I-10 to serve northbound traffic along SR 121 which are proposed to address the immediate capacity need at this critical interchange for Baker County, FL.
Travel Time Savings
| Network-wide Comparison |
Design Year 2040 No-Build Alternative |
Design Year 2040 Interim Concept 1 Alternative |
Difference |
| Total Delay (hrs) |
AM Peak |
86 |
30 |
-65% |
| PM Peak |
2,799 |
55 |
-98% |
| Total Travel Time (hrs) |
AM Peak |
138 |
82 |
-41% |
| PM Peak |
2,871 |
127 |
-96% |
| Average Speed (mph) |
AM Peak |
11 |
19 |
73% |
| PM Peak |
1 |
17 |
1600% |
FDOT Emergency Travel Alert: For information on the current situation, please visit the following
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