Michigan DOT says new traffic study justifies new Detroit River bridge

February 18, 2010
By Peter Samuel

Michigan DOT has released traffic projections for the proposed new international bridge over the Detroit River, for which it recently issued a request for proposals of interest in a PPP. Major finding of the traffic study led by Wilbur Smith Associates is that the recent dramatic declines in traffic on the crossings justify a 2035 projection about ten percent lower than before.

That would make the forecast of average weekday traffic on the new DRIC bridge 34.6k versus 38.2k in a preliminary study released with the environmental impact statement Nov 2008.

Michigan DOT (MDOT) officials say in a statement accompanying the release of the traffic study that its findings reaffirm the need for the additional crossing despite the current depression in traffic.

Michigan state transportation director Kirk T Steudle is quoted: "We welcome the opportunity to have the traffic projections that were used for the FEIS reaffirmed by a new investment-grade traffic study. This new study not only confirms the importance of the existing international crossing but also reaffirms the need for a new crossing in the Detroit-Windsor corridor within the next five to 10 years in order to support trade between the United States and Canada."

Like most Wilbur-Smith studies this seems to be a meticulous examination of the factors bearing on future traffic and a conscientious effort to put the best numbers on it. However the report notes  "inherent uncertainties.. especially as a result of the volatility of many factors (including) the current financial crisis and economic turmoil." (p6-19)

The report as released today on traffic-only doesn't directly address whether the new bridge is needed or whether it is financially viable.  

The revenue part of the study, still to be completed, should throw more light on the need and viability of the new crossing.

Strong competition with four crossings

There's a highly competitive situation with three and potentially four crossings, the study reports.

The existing crossings are from north to south:

- Blue Water Bridge (BWB), 6 lanes Port Huron to Sarnia connecting I-69 to H402 and competitive for trucks especially to Chicago, carries 32% of the trucks, 23% of the cars, 25% of total vehicles

- Detroit Windsor Tunnel (DWT), 2 lanes competitive for car trips downtown Detroit-Windsor, carries 38% of the cars, only 3% of the trucks, 28% of total vehicles

- Ambassador Bridge (AB), 4 lanes, getting a direct connection off the I-75 in Detroit and connected to a signalized Huron Church Road Windsor, the giant for trucks taking 64% of them, and 39% of the cars, 45% of total vehicles

Just 3km (1.8mi) downriver, or south of the Ambassador Bridge is the chosen and permitted site for the new Detroit River International Crossing (DRIC) bridge, a proposed 6-laner.

The bridge, a cable stayed structure, is estimated to cost $812m, the US customs/immigration inspection and toll plaza $474m, an interchange with I-75 $451m, the Canadian plaza $523m, and a 11km (7mi) 6 lane Windsor-Essex Parkway connecting the Canadian side of the bridge to Highway 401 about $1500m. The Canadians are managing the big parkway project, much of it in shallow cut and cover tunnels, quite independently of the bridge and work is due to start on it this year.

Jointly Michigan and the Canadian national government are exploring one or multiple public-private partnership arrangements including a toll concession for the bridge, the I-75 interchange and parts of the two plazas.

Expressway to expressway connections

A major competitive advantage of the new DRIC bridge will be the expressway-to-expressway direct connections on either side as opposed to the many traffic signals on the Windsor side of the Ambassador Bridge along Huron Church Road. the new bridge is slightly more direct too for traffic south on I-75 and time savings are put at 2 to 8 minutes. For traffic west to Chicago there are no time savings.

The Wilbur Smith study forecasts that the new bridge - assumed to open in 2016 - will attract 34% of 2035 traffic, including 27% of car traffic and 44% of trucks.

It estimates that will mean a 31 percentage point (pp) reduction in the Ambassador Bridge's current share of 64% of truck traffic by 31pp to 33% and a reduction in the Blue Water Bridge's 32% by 13pp to 19%.  The Detroit Windsor Tunnel would keep its negligible 3 or 4% of trucks.

The new DRIC bridge is estimated by WSA to get 27% of car traffic, about 12pp from the Ambassador Bridge and 11pp from the Detroit Windsor Tunnel and 4pp from the Blue Water Bridge.

The projected average weekday traffic of the new bridge is not large: 2016 18.7k, 2025 26.5k, 2035 34.6k. The split is almost 50% cars, 50% trucks, an extremely truck-intensive facility. But all those figures are still modest for 6 lanes.

We don't have the revenue part of the study so far, but applying current toll rates on the Ambassador bridge of about $4 for cars and $22 for average trucks to the 2025 forecast of 4.42m cars and 3.92m trucks you get cars generating $17m and trucks $86m for total toll revenue of $103m/year.

In favor of the new DRIC bridge is the aging of the Ambassador Bridge, its increasing unsuitability  for heavy trucks, and the unwillingness of governments on both sides to allow construction of a new modern Ambassador alongside.  

COMMENT: Some time not long after the new DRIC bridge opens it might make sense to convert the old Ambassador to a cars and light vehicles only bridge that would stress its 80 year old 'body' much less than the present lines of tractor-trailers.

That would leave the heavy trucks to be divided between the Blue Water Bridge and the new DRIC - making the DRIC more viable financially.

230 page traffic-only study led by Wilbur Smith Associates:


project website:


Windsor Essex parkway:


ADDITION: An official of the Ambassador Bridge objects to our characterization of their bridge as increasingly unsuitable for heavy trucks. He says the company has Masters and Majewski, well known bridge engineers out of Pittsburgh do a detailed inspection every year, and that "many millions of dollars" are spent to fix problems they find or anticipate. The bridge has to be certified as in safe condition by authorities on both sides of the border.

TOLLROADSnews 2010-02-17 ADDITION 2010-02-18 14:45

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