Traffic engineers are wrong. Again.

The Peninsula Traffic Study of 2006 was rejected in large part because of its recommendations for downtown streets like Franklin Arterial. The study, which was written by Gorrill-Palmer, a local traffic engineering firm, predicted that Franklin might need to be widened to as much as eight lanes to accommodate an exaggeratedly large amount of future traffic.

Neighbors rejected the study because it focused only on moving single-occupant motor vehicles, and many also also questioned the validity of the study's traffic projections. Now, updated data reveals that Gorril-Palmer's projections were wildly off the mark.

Consultants from Smart Mobility, the firm that's helping the city determine a more humane future for Franklin Street, prepared the above chart to show actual traffic data from the past 20 years, plus a range of projections for the future.

The outlying projection at the top is the one Gorrill-Palmer made for the Peninsula Traffic Study. The green line way below that one shows a projection with 20% growth in traffic, which Smart Mobility considers "unlikely." The red line shows 10% growth, a "realistic high count" for 2025 that would essentially put Franklin's traffic levels back where they were through the 1990s.

During the 2000s, a period of increasing gasoline prices and infill development on the peninsula, Franklin Street’s traffic declined substantially, to the levels of the mid-1980s. Gorrill-Palmer's projection was apparently made by extending the growth in traffic during the 1970s and 1980s into the 21st century, with no regard for underlying trends in demographics or energy prices. By their logic, the Dow Jones index should be over 20,000 by now.

In other words, if you're inclined to believe a traffic engineer's numbers, perhaps I could interest you in purchasing some General Motors stock? You'll be rich by 2025, I guarantee it!

Smart Mobility even hedges its 10% growth projection by calling it a "high count" - the upper range of what's likely to happen. Who's to say that motor vehicle traffic on Franklin Street won't continue its recent decline?

These updated data and projections demonstrate definitively that the projections of MDOT and other traffic engineering firms are, at their best, bad math. At their worst, they amount to an unholy voodoo science that's hell-bent on destroying our cities and neighborhoods.