  In the control of vehicular platoons, the disturbances acting on one vehicle
can propagate and affect other vehicles. If the disturbances do not amplify
along the vehicular string, then it is called string stable. However, it is
usually difficult to achieve string stability with a distributed control
setting, especially when a constant spacing policy is considered. This note
considers the string unstable cases and studies disturbance propagation in a
nonlinear vehicular platoon consisting of $n+1$ vehicles where the (virtual)
leading vehicle provides the reference for a constant spacing policy. Apart
from the communications between consecutive vehicles, we also assume that each
vehicle can receive information from $r$ neighbors ahead, that is, the
vehicular platoon has communication range $r$. For the maximal overshoot of the
inter-vehicular spacing errors, we explicitly show that the effect of
disturbances, including the external disturbances acting on each vehicle and
the acceleration of the leading vehicle, is scaled by $O(\sqrt{ \left \lceil
\frac{n}{r} \right \rceil})$ for a fixed $n$. This implies that disturbance
propagation can be reduced by increasing communication range. Numerical
simulation is provided to illustrate the main results.
