In 2014, GFParsons proposed for value engineering, a Type AB2 (or folded) parallel flow diamond interchange (PFDI) design for the US-20/I-475 interchange in Toledo, Ohio. The Ohio DOT was 90% complete with the final construction plans for a single-point urban interchange (SPUI) at the time.

The PFDI design would have potentially saved $40 million (est.) after GFParsons fees. The resulting PFDI would have saved the existing bridge with an estimated 50+ year life and involved minimal impacts to existing roads. The PFDI would also have maintained the existing I-475 ramp spacing as well as provided a higher level of service (i.e. less vehicle delay) over it’s 20-year service life.

Click to open the GFParsons’ PFDI proposal to ODOT.

Proposed final PFDI concept for US-20/I-475
Preliminary PDFI concept overlaid onto ODOT SPUI design

Updated Jul 18, 2015: The Ohio DOT will build the SPUI after all. GFParsons proposed the PFDI in summer 2014 but ODOT said no because they didn’t have time to change plans by January 2015. GFParsons waited for the project to be awarded for construction (June 2015) so the contractor could submit the PFDI as a value engineering change proposal (VECP) whereby the contractor would split the $14 million (est) savings 50/50 with ODOT. The contractor chose not to because it would have meant layoffs for bridge workers (who will be kept busy instead building a substandard interchange with unnecessary bridge and retaining walls).

PFDI simulation starting 45 mins. into 2035 PM peak hour.
PFDI closeup view 2035 peak hour.

Performance (design year 2035):

~4,600 veh per hour AM LOS B

~5,800 veh per hour PM LOS C

Unrealized est. savings: ~$40 million (including engineering + right-of-way)

Planned project is to replace existing folded diamond with single point urban interchange (SPUI).

* PFDI will operate at higher level of service than SPUI.

* PFDI keeps existing bridge (has 95% sufficiency rating).

* PFDI maintains straight roadway. SPUI will be constructed between reverse curves and on vertical crest curve with both conditions limiting sight distance and below national best practice standards for SPUI design.

* PFDI maintains existing ramp spacing on Interstate (to northern US-23 system interchange). SPUI will degrade Interstate operations by reducing ramp spacing to 400-ft below ODOT standard minimum. Location: Toledo, Ohio

Click here to see site on Google Maps.