In response to a recent post on LinkedIn from a South Asia colleague about the merits of UVSS, I felt obliged to post the following response. I hope you find it useful.
[name redacted], you raise a very important question, which relates to the broader concept of under-vehicle searching in general. As a frequent visitor to both India and Pakistan, I am dismayed at the emphasis that is placed on under-vehicle searches at the expense of checking the credentials of the vehicle driver or examining closely the inside of the vehicle. The overwhelming majority of VBIEDs have no evidence of their installation that is visible either with a UVSS or under-vehicle search mirror; UV search is a technique specifically for UVIEDs. The overwhelming majority of car bombs are large VBIEDS, which are built not under, but into the vehicle, hidden in the boot or the rear seat area, and can only be identified by looking for a specific cluster of clues. A UVIED is a precision device, intended to kill a specific single target. The VBIED is what we should be most concerned about as it is a mass–casualty device.
The UV search concept, I believe, originated in the UK, when terrorist groups here began to place small IEDs (Around 2kg of HE sufficient to kill/maime the driver) under vehicles near the driver seat in the 1980s. They were activated by a tilt switch. Soldiers, police officers, prison officers, judges, politicians, lawyers, opposition figures etc were the specific target. There were something in the region of 500 such attacks over a 25-year period. The tactic continues to this time, but on a very much reduced scale, and other groups, such as single-issue activists have tried to emulate this practice, with limited success. In some countries, similar devices have been place on car windows in the guise of drinks cartons etc. or near car fuel tanks.
As always, any savvy adversary carrying out pre-attack reconnaissance on a facility and observing that vehicles searches are confined to UV will be encouraged by the fact that he is likely to be able to get his VBIED past the checkpoint to the target. And remember, of course, that many adversaries have undertaken specific training in IED attack so know what to look for.
Where UV searching does have its place is if you believe the underside of the vehicle is used for moving small arms into the facility, intruder infiltration, or contraband smuggling. There is also a chance that a proxy IED may be placed underneath, but the threat assessment or design basis threat should tell you if the latter is a credible scenario. In general, however, the focus should be on regular VBIED search unless there is a specific reason to do otherwise.