As the extension was planned in 1968, plans were also made for a freeway bypassing Tampa Bay to the east. The bypass was initially planned to be designated I-75E, and was to split from I-75 near Wesley Chapel and rejoin it just north of Ellenton. However, in 1972, it was determined that maintaining the main route of I-75 through Downtown Tampa would eventually require major improvements to the existing infrastructure to handle through traffic. As a result, it was decided that I-75 would instead follow the bypass route. FDOT could have renumbered I-75E into what could have possibly been I-75W, but due to a 1973-based AASHTO rule indicating that suffixed routes were to be renumbered to reduce motorist confusion, the option of renumbering I-75E into I-75W was scrapped. Instead, the I-75E designation was renumbered to what is known today as I-275, and both the I-75 and I-275 designations were swapped into their current configuration in 1973. I-75 reached as far south as 38th Avenue North in St. Petersburg when the designations were switched. Despite the designation switch, both freeways' hidden designations still reflect the originally planned routing, with I-75's SR 93 designation following I-275, and the current route of I-75 on the bypass being designated SR 93A. Construction on the bypass segment of I-75 began in 1979.