This looks to be an Mobile Explosion Containment Vessel pulled by another vehicle.
http://www.uxb.com/pages/explosion_containment.html
MBPD Explosion Containment Unit
By Tyco @ 2013-04-29 08:09:57
Links: en.wikipedia.org
Unrated
Scavenger Hunt: Celebrate Boston: Bomb Squad Vehicle (Note 2)
Categories
Blog Posts
kjfitz
@ 2013-04-29 08:42:24
BOOM! kudos!
Tyco
@ 2013-04-29 08:56:24
Thanks!