By Charles C. Roberts, Jr., Ph.D., P.E.
vehicle accidents can occur as a result of defects and are often at the root of an insurance claim. It is not unusual for an insured to blame an automo- bile accident on a defect related to a vehicle. Insurers hear policyholders bemoaning that their brakes failed, the
accelerator stuck, a tire detached, and similar allegations of malfunction. The claims analyst typically investigates the existence
of a defect to determine liability or the possibility of subrogation.
The extent of the many potential defects that may exist in an
automotive vehicle is beyond the scope of merely one article.
Let’s examine some case studies of actual accidents involving a
defect in the throttle control system.
Below, Figure 1 shows three typical throttle control systems
in automobile. The mechanical system is a classic, having been
developed since the early days of the automobile. Rod linkages
are connected to the throttle plate to actuate the throttle with a
return spring whose purpose is to close the throttle plate once
the driver’s foot is removed. The cable throttle control system is
a more recent design whereby a cable controls the throttle via a
pulley. A torsional spring returns the throttle plate to a closed
position once the driver’s foot is removed. The third system is a
“fly by wire” or an electronic control system where an accelerator
position sensor sends a signal to an electronic control module
(ECM), that sends a signal to a throttle position motor, which in
turn sets the throttle position.
improperly installed, the wrong size, or improperly designed.
Downloading the sensing diagnostic module, the modern vehicle’s “black box,” can provide evidence of the malfunction. In
one instance, a dealer had substituted another floor mat for the
factory installed one, causing the malfunction. In another case,
the insured supplied the floor mat. Clearly subrogation potential
is dependent upon the claims analyst’s investigation tying down
the facts regarding the floor mat placement.
The following case studies illustrate problems with throttle
control systems that have caused an accident. A common throttle
system malfunction is the engagement of the accelerator pedal
in the vehicle floor mat as shown in Figure 2A above and to the
right. The driver of this vehicle pressed the accelerator pedal to
the floor, and when the pedal was released, the vehicle continued
to accelerate at high speed, eventually causing an accident.
There are several reasons for the engagement of an accelerator pedal under a carpet. The carpet could be out of position,
Figure 2B shows an accelerator pedal engaged in the polymer wear pad at a sewing seam. When the accelerator pedal was
pressed, it readily engaged in the wear pad, which resulted in
uncontrolled acceleration and an accident. This is obviously a
Another cause of throttle malfunction is corrosion of throttle
linkages. You will discern in Figures 3A and 3B (on the next page)
a small ball joint that is part of a throttle assembly near the throttle
plate. The ball joint eventually became difficult to articulate because
of corrosion, causing the throttle to remain open after the accelerator pedal was released. This resulted in an accident, and in this particular case, corrosion-resistive plating of the metal parts was insufficient and was consequently found to be a manufacturing defect.