may
2019
feature article
downhill braking. In addition, there are no wide-
ly accepted standards for golf cart path design,
and inadequate recommendations provided by
car manufacturers for maximum path slope and
minimum turning radii are ambiguous with warn-
ings that refer to “steep grades” and “sharp turns”
without quantifying these terms. This separation
between golf cart design standards, which only
require dynamic braking tests on flat ground, and
sloped car path design, which lack any specificity,
causes golf carts to be routinely driven on poten-
tially dangerous terrain that is not addressed by
the ANSI golf car standard. In addition, while the
ANSI standard requires that a golf car’s maximum
speed not exceed 15 mph on level ground, that
speed can easily be exceeded when traveling
downhill.
To evaluate the potential hazards of creating
golf carts equipped with brakes on only the rear
axle wheels, Technology Associates has analyzed
the braking of a two-axle vehicle, equipped with
brakes on either or both of its axle wheels. In ad-
dition, dynamic two-dimensional simulations of
a braking golf cart traveling downhill have been
created to study vehicle dynamic stability (and
resulting rollover propensity). For this compari-
son, we introduce the term “braking efficiency”,
defined as the actual vehicle braking decelera-
tion, divided by the braking deceleration of the
same vehicle with brakes on all four wheels (i.e.
the maximum possible braking deceleration for
a given slope and coefficient of friction). Thus,
by definition, the case with braking on all four
wheels yields an efficiency of 100%.
For either case where only the front or rear
wheels are braked hard, braking efficiency de-
creases rapidly as the downhill slope increases,
such that at path down slopes over 20 degrees,
the brakes are no longer able to prevent the golf
cart from accelerating downhill. For slopes of 10-
15 degrees, with which golf carts must currently
contend, placing brakes on only the rear axle
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WWW.GOLFCAROPTIONS.COM
wheels provides only 25-37% of the braking that
could be achieved with brakes on all four wheels.
Therefore, equipping a car with brakes on only
the rear wheels reduces the available braking effi-
ciency significantly when compared to a vehicle
with brakes on all four wheels.
Dynamic simulations indicate that golf cart yaw
instability (and subsequent rollover) is not like-
ly on flat ground at speeds under 15 mph and
therefore will not manifest itself during ANSI
brake performance testing. However, for a vehi-
cle with brakes on the rear wheels only, when the
initial speed is 17 mph or higher, yaw instability
can occur when traveling down a 10-degree slope
when modest steering inputs are made. Such loss
of control could easily cause the car to leave the
path and either collide with or tip over, nearby
obstacles and path curbs.
However, when the front axle wheels, or all four
wheels, are braked hard enough to lock them,
there is no significant deviation from straight
path travel. Therefore, if the cars were equipped
with front brakes (either by themselves only, or in
combination with rear brakes) this yaw instability
problem would be significantly reduced if not en-
tirely eliminated, and the risk of rollovers would
be greatly reduced.
Articles Cited
Note: This article summarizes research from several of
Technology Associates’ peer reviewed journal articles cited
below
• Seluga, K., Baker, L., & Ojalvo, I., “A Parametric Study of
Golf Car and Personal Transport Vehicle Braking Stabili-
ty,” J Accident Analysis & Prevention 2009; 41:4:839-848.
• Seluga, K., & Ojalvo, I., “Braking Hazards of Golf Cars
and Low Speed Vehicles,” J Accident Analysis & Prevention
2006; 38:6:1151-1156.