🚀 go-pugleaf

Most automobile alarm systems today seem to include a "motion" or
"impact" sensor -- either a simple weighted spring, or a sophisticated
electronic device -- which sets off the alarm if the car is hit or
jarred (as, for example, during an attempted tow).

I seriously question whether these sensors are really useful.  I tend to
think they are more trouble than they are worth.

I would appreciate any comments on the following ideas:

==> A motion/impact sensor can tell whether someone has bumped into your
    car.  If you return to your car and see that the alarm has not been
    set off, you know you needn't inspect it carefully for damage.

    On the other hand, I would think that an alarm would tend to scare
    the "hitter" away -- where otherwise he might (and I repeat *might*)
    leave a note.  In such a situation, the alarm would be counterpro-
    ductive.

    As far as alerting the car owner so that he can go out to his car
    and possibly identify the other car before it leaves the scene, I
    doubt this would work unless the owner could get out to his car
    within a few seconds at most.

==> A motion/impact sensor can set off the alarm if someone tries to
    tow your car away.

    On the other hand, a thief who is brazen enough to tow away a car
    is not likely to be deterred by an alarm.  (Some people may use
    this point as an argument against *all* alarms, of course.)

    Besides, just because a car being towed has an alarm sounding off
    doesn't mean the car is being stolen (maybe it was parked illegally
    and is being towed legitimately).  So, neighbors or passers-by may
    not necessarily take any action (except to curse the racket being
    produced by the alarm).

    I think a much more effective measure to discourage illegal towaways
    would be to engrave the VIN number all over the car (so as to make
    it less attractive to the "chop shops").

==> Motion/impact sensors contribute heavily to false alarms (especially
    with cars in parking structures), thus fostering a "cry wolf" image
    and eroding public willingness to take car alarms seriously.

What do other people on the net feel about motion/impact sensors?

Since I know the subject of car alarms is almost a "religious" issue,
let me emphasize that I am asking specifically for opinions about
motion/impact sensors -- not car alarms in general.

If you do feel impelled to speak to the general issue of whether car
alarms are worth having, go ahead (how could I stop you, anyway? :-}),
but *please* be sure to change the "Subject:" line in your followup.
-- 
Rich Wales // UCLA Computer Science Department // +1 213-825-5683
	3531 Boelter Hall // Los Angeles, California 90024 // USA
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