With the driver sitting in a normal driving position, the top of the driver's helmet shall be at least two inchs (2 in) below a straight line, a.k.a., broomstick, extending from the top of the rollbar forward to the highest structrual part of the vehicle. If factory documentation indicates that the A-pillar is structrual, it may be used as the forward point for the test. Otherwise, the top of the forward shock mount shall be used.