(DOS) (listed in Table C-1 in Appendix C) are provided in Table 3. Manufacturers can provide
guidance on available options and will make recommendations that will enhance barrier operations.
Operational Cycle. The frequency of operation must be considered in the selection
process. Where traffic flow is light, a manually operated or removable passive system may work
well at considerable savings. However, for high-traffic flow conditions (especially during peak
hours), an automatically controlled system designed for repeated and fast open and close operation
(pneumatic or hydraulic) would be more desirable. The use of one or more barriers at an entry point
can also improve throughput.
7.2.16 Methods of Access Control. When selecting an active barrier, consider how vehicles
will be allowed access. If a vehicle must be searched for explosives, a sally port design should
be used, which will trap the vehicle between two active barriers while it is being searched. This
will prevent the vehicle from proceeding into the secured area before it has been searched and
prevent escape (see Figure 4). Access control can be accomplished with a staffed guard station
or, remotely, using card or biometric access control devices that automatically activate the
barrier (subject to random searches). The barrier can also be operated from a protected location
other than the entry control point, using CCTV and remote controls. Access control systems are
available as options from vehicle barrier manufacturers (see Table 3). Vehicle-sensing loops on
the secure side of the vehicle barrier should always be included to prevent activation of the
barrier until the vehicle has completely cleared the system. If card access control systems are
used, procedures must be included to prevent tailgating (authorized vehicle must wait until the
barrier has closed completely before proceeding).
Cost Effectiveness. Tradeoffs on protective measures may include:
a) Locating the vehicle barrier to provide optimum separation distance;
b) Slowing down vehicles approaching the barrier, using obstructions or redesign of the
c) Barrier open to permit access vs. closed to prevent access;
d) Active vs. passive barriers;
e) System-activating options: manual vs. automatic, local vs. remote, electrical vs.
f) Safety, RAM characteristics.