After the Wallace Tunnel was built, many motorists had traffic accidents there. It is something we motorists have become familiar with here in Mobile. The curve in the tunnel somehow confuses some drivers or sneaks up on them, and they end up getting in wrecks and clogging the tunnels.
Back in the mid-70's, local leaders wanted to slow down that flow of traffic to prevent accidents, so they installed the first speed alert system. You can watch the local news report from that era below (uploaded by Youtuber Roland Fields.)