The Colorado Department of Transportation has conducted a study on the goods and the bads of transporting hazardous materials through the Eisenhower/Johnson Memorial Tunnels. Running trucks through tunnels is always a risky business and this study looked at all of the angles. If something did happen inside the tunnel, that access would be shut down for a very long and inconvenient time.
Right now, hazmat trucks are supposed to use the Loveland Pass when it is open otherwise use the tunnels at the top of each hour when the Pass is closed. The tunnels are already equipped for fire and hazmat incidents and have never been closed for longer than 10 hours thanks to these systems. They also took into consideration the dangers of inclement weather on the Loveland Pass and how trucks are also at risk up there.
Many options have been thrown out there like allowing hazmat trucks through during the quiet hours and adding different fire-suppressions to the tunnels for added safety. Click the link below to learn more about this.