Mobile Crime Scene
The Mobile Crime Scene is usually a dilapidated RV that runs well enough to move its tweaker occupants to various locations around town. RV's are preferred since their classification as a "home" makes search warrants more difficult to obtain. The term can also apply to creepy cargo vans or other vehicles that look to be used for nefarious purposes.
If something smells funny in the neghborhood you should check if the tweakers have set up a Mobile Crime Scene and started cooking up meth.