The tunnel is inherently most vulnerable to hazardous materials due to the limited ability of vehicle occupants to avoid toxic lumes tn the tunnel. The. ventilation system inside the tunnel might contribute to (exoacethbaotel or impede escape with respect to haozmot incidents, ll the ventilation system were kept on: the a(liirt supply could ton any litteess. and make the conditions in the impacted section ol the tunnel worse, tn thee, case ol toxic g90a5s and liquid spills, it the ventilation syhstem were kept on, one has to consider the possibility (and resultant consequences) of toxic gases being discharged from, or dtistrtibuted through, the ventilation system The cdliillutiton ol the hazardous materials would be a0 lunctton ol the number ol ventilation zones in the tunnel aellectecl by the release. For spills ol toxic liquids, the impact could be significant because g9r1a0vitthy would allow the spill lto ttcwel toward the lowest point in the tunnel, consequently couslng more ol the toxitc gases to llow into the ventilation system. While the video surveillance system would allow tunnel managers to identity dangerous situations quickly, the number ol individuals that might be tHtaopped in the tunnel and the lock, oalt any sale escuape portals lrtom the tunnel decrease the likelihood of escape. Escape portals aore ptesent in most modern tunnels longer than f5)(X) meters, but ptesently not installed in the Windsor Tunnel.

PROPOSED RECOMMENDATION:

The route under Cobo Haell is a0 function Ool the con•guration ol the route that creates a0 "de laocto" tunnel, and, a05s such, thete ts a<1 need to ptolteezt the acltctcent downtown awreae ol Detroit, 05 well aUs the highway tnlraostructure. An explosion unttdemt tlhlue: budding Would pose an obvious rtsk to the building structure a(mnd to people inside and Immediately outside ol the building, 05 well ()5 to those on the a()llleétr‘tled htghwnuy Marty ol the types aotl plumes. haem hu/Jnmat toeleoase resulting from a crash near. 0|: under, Coho Hall have the [p)OotlEenHtltIOol to impact Dettoit's highly populated downtown business district.

PROPOSED RECOMMENDATION:

0 Restrict all placarded vehicles.

the lowemred highway coulcl conline spills ol gas, extend the haozcudous concentration lacuttthet clown the

rtouadwuay and delay the dissipation ol potentially hazardous plumes. Sale escape routes. would l[z:0e limited to existing lurldets mulluang M-tlO's vVeCtltlilCcUal walls, thus limiting sole escape toutes lot vehtcle occupants. l'he ttsk would be reduced on road sections that are loweetr‘ecdl but with sloped, rather than vertical, walls. Based on analysis aotl thoe dutrnt, wlhutch exarrttned the potential lort hazardous gas (Class 2 maotetiaull involved in aon accident to combust or vaporize rapidly -‘ presenting the potential for high risk Closs 2 (Gases) hazardous materials also should be restricted.

0 Restrict Classes 1, 2, 3, 5, 6 and 8.