Confronting the underride issue : it is better to prevent an accident, or lessen its severity?

As 2/3 of car-truck fatal accidents in the USA occur at night, a better conspicuity of trucks could prevent part of these. Suggestions for placing lamps and reflectors on side and back. Over 85% of injuried accidnets did not involve penetration of passenger compartment. Guards would not be effective in those cases, is supposed.