The hairpin ramps at I-10 and I-35

Also see: Interstate 10 San Antonio double deck | Interstate 35 San Antonio double deck

The elevated structures on Interstate 10 and Interstate 35 are very well designed, with one exception: the connection ramps at the IH-10/IH35 interchange. The eastbound IH-10 to northbound IH-35 and southbound IH-35 to westbound IH-10 ramps both have extremely narrow radii. The ramps were built with extra-thick and extra-high concrete guardrails to prevent vehicles from breaching the guardrails during collisions.

So why were these ramps so poorly designed? My best guess is that it was a right-of-way issue that contrained the geometrics of the interchange. Unfortunately, a similar situation has just occurred in the planning phase of the future stack IH-30/Loop 12 in west Dallas. Because of a low income housing struture in the way of the interchange, a ramp is being designed with a 30 miles-per-hour design speed. This is very unfortunate, because in a logical and reasonable world, an easily replacable low-income apartment building should not compromise a $100 million interchange that will be around for 50+ years. But that's the way the system works.