I-95 and Route 123 (Exit 160) Interchange Improvements

This project is the first Progressive Design Build (PDB) project in Virginia, involving the selected Design-Build team in the very early stages of design. The project involves improvements at the I-95 Exit 160 interchange at Route 123 (Gordon Boulevard). For the first phase of the project, T3 was responsible for traffic data collection, screening analysis of alternatives, traffic operational and safety analysis, and preparation of an Interchange Access Report (IAR) for FHWA approval.T3 served as a traffic engineering subconsultant on this PDB project. T3 managed a large data collection effort involving peak hour turning movement counts and 48-hour automatic traffic recorder (ATR) counts at 31 locations. They prepared balanced traffic volumes to provide a baseline of existing conditions for the study area. They then evaluated traffic volume projections used by adjacent traffic studies and compared historical annual traffic growth with COVID-19, pandemic-related traffic changes to recommend future traffic volumes and analysis years. T3 met with both VDOT and FHWA to establish the projection methodology for approval, then developed design year forecasts.

T3 performed a scoping level traffic operational analysis to evaluate geometric, operational and constructability conditions in order to determine any design and operational elements required for the project. T3 analyzed traffic operations using Synchro, SimTraffic, and VISSIM. They analyzed safety by preparing Interactive Highway Safety Design Model (IHSDM) models for various design options to establish the preferred alternative.

T3 developed an Interchange Adjustment Report (IAR) for the modified access on both interstate and non-interstate roadways, including a complete alternatives analysis with identification of a preferred alternative in conjunction with the NEPA Document. The IAR required approval by both VDOT and FHWA, so T3 coordinated regularly with both agencies and prepared a progressive chapter submittal schedule to allow VDOT and FHWA to review sections about once per month in order to accelerate the approval process. T3 prepared an LD-459 Framework Document to detail the purpose and need, proposed measures of effectiveness (MOEs), and proposed methodology.