In July 2020, the Florida Department of Transportation received approval from the Federal Highway Administration for the Interchange Modification Report, supporting the implementation modifications, hereafter referred to as the Alternative Technical Concept 32 or ATC 32. The improvements are along Wekiva Parkway extending from Orange Boulevard to west of I-4 in Seminole County, Florida.
This IMR compares traffic operations for the ATC 32 Concept, and the Request for Proposal or RFP Concept.
The purpose of this IMR is to demonstrate that the ATC 32 Concept is performing equal to or better than the RFP Concept and has satisfied the FHWA policy points.
The ATC 32 Concept modifies the RFP concept with the following modifications:
The on-ramp from County Road 46 A to eastbound I-4 connects to I-4 north of State Road 417/429 in the proposed modification. This modification preserves the existing braided ramp and removes a proposed bridge.
In the ATC 32 Concept, the on-ramp to southbound State Road 429 from International Parkway is relocated south, along International Parkway, of its original access point. This modification allows the left-turn movement to be signalized as part of the Tight Urban Diamond Interchange with International Parkway and removes a bridge over Wilson Road.
The northbound State Road 429 off-ramp to International Parkway no longer crosses over International Parkway in the ATC 32 Concept which removes the loop ramp. Thus, this modification removes a bridge over International Parkway. Vehicles intending to travel north on International Parkway will no longer access International Parkway via a free-flow movement; instead, access would be controlled by a signalized intersection as part of the overall Tight Urban Diamond Interchange with International Parkway which will improve pedestrian and bicycle safety on International Parkway.
In the ATC 32 Concept, access to the State Road 417 southbound on-ramp from International Parkway is provided closer to the crossing of State Road 429 and International Parkway.
The State Road 417 northbound off-ramp onto International Parkway begins diverging from southbound State Road 429 west of I-4 in the proposed modification. This modification eliminates the bridge over State Road 417 required in the RFP Concept. Additionally, by relocating this off-ramp west of I-4, westbound drivers are more easily able to anticipate the lane they must be in to access International Parkway. Further, the RFP Concept involves a decision point just west of the I-4 underpass where the ramps to International Parkway from the westbound I-4 ramp split. The proposed modification removes this split and allows the separation of local and system interchange ramps.
Access to the eastbound I-4 ramp to southbound State Road 429 is provided further north along I-4, which is closer to State Road 429 and is separated from the off-ramp to southbound State Road 417. The I-4 loop ramp is shifted to the west, which reduces the number of bridges required for this interchange.
The eastbound I-4 ramp to southbound State Road 417 utilizes milling and resurfacing of the existing ramp up to the proposed Ramp M 2/State Road 46 Ramp split. The geometry of Ramp M 2 is similar to Ramp M M 2 in the RFP Concept; however, the Ramp M 2 radius is increased in the proposed modification. The ATC 32 Concept maintains the existing drivers' expectancy for these movements since we are not deviating from the current ramp configuration.
In the proposed modification, the eastbound I-4 off-ramp providing access to State Road 46 is combined with the eastbound I-4 ramp to southbound State Road 417. This modification utilizes the existing bridge and removes a proposed braided ramp bridge. The M 3 off-ramp is maintained as a two-lane ramp and the weaving for the future E E 4 ramp is eliminated.
The radius of the State Road 417 northbound off-ramp to eastbound I-4 has been increased. This change in radius improves sight distance.
The Ramp N N 2 bridge crossing over State Road 417 in the RFP Concept is relocated westward in the proposed modification to cross over State Road 429 adjacent to I-4, thereby eliminating the conflict with the Duke Transmission powerlines. Ramp N 2 is curved around the I-4 eastbound loop ramp to southbound State Road 429. Further, the approach to westbound I-4 runs adjacent to I-4, allowing vehicles to accelerate up to the I-4 traveling speed before getting on westbound I-4. The merge is kept separate from the northbound State Road 429 ramp to westbound I-4.
The westbound I-4 collector-distributor system providing access to the ramp for southbound State Road 429 and the ramp for southbound State Road 417 is shifted slightly west to accommodate the proposed modifications to the interchange configuration; the basic geometry of the collector-distributor road and access points are unchanged.
The northbound State Road 429 to eastbound I-4 ramp is curved around the westbound I-4 to southbound State Road 417 loop ramp. In both scenarios, this ramp merges with northbound State Road 417 to eastbound I-4 ramp before merging with I-4.
The proposed modification to the westbound I-4 ramp to southbound State Road 429 leaves the ramp largely unchanged. However, the modification provides a longer approach to State Road 429 and separates the ramp from the Tight Urban Diamond Interchange ramp at International Parkway.
The proposed modification to the ramp from the westbound I-4 collector-distributor system to eastbound State Road 417 leaves the ramp largely unchanged with the exception that it is shifted westward to accommodate the western shift of the collector-distributor system and I-4. This ramp is separated from the eastbound I-4 ramp to southbound State Road 417, which makes for two single-lane merges on southbound State Road 417 rather than a dual-lane ramp merge.
The IMR provides the traffic operational analysis for the opening year and design year to demonstrate that the ATC 32 Concept is better than the RFP Concept. An analysis of the ATC 32 Concept was performed in accordance with the related MLOU and the FDOT’s Interchange Access Request Users’ Guide.
The 2020 IMR ATC 32 Concept satisfies the FHWA’s Policy on Access to the Interstate System and provides the same or better traffic operations when compared to the RFP Concept.
A comparison of the ATC 32 and RFP Concepts level of service by segments was performed and shows the ATC 32 Concept has a higher percentage of segments within the acceptable level of service range, A to D, and a smaller percentage of segments operating at a level of service E and F. Overall, there are 15 segments with a better level of service in the ATC 32 Concept.
The network-wide output produced by the Vissim models provides additional insight into operational conditions. For the AM period, the 2043 ATC 32 Vissim model is performing 1% to 2% better than the 2043 RFP Vissim model. For the PM period, the 2043 ATC 32 Vissim model is performing equally as the 2043 RFP Vissim model.
A detailed safety analysis was conducted using I Sat E. The analysis showed a reduction of 7% in the total number of expected crashes when comparing the ATC 32 to the RFP Concepts. This results in a 19-million-dollar economic saving. The ATC 32 Concept showed a reduction in crashes in each severity distribution. fatal, severe injury, moderate injury, minor injury, and property damage, when compared with the RFP Concept.
In conclusion, the comparison of the ATC 32 and the RFP Concepts show that the ATC 32 Concept will provide a better level of service and safer operating conditions. The proposed ATC 32 Concept modifications are not anticipated to have a negative impact on operations or safety on the I-4 mainline or adjacent interchange when compared with the RFP Concept. This IMR was approved by FDOT Central Office and Federal Highway in July 2020.