For motorists seeking greater protection in crashes, test results released Sunday by the insurance industry show the benefits of paying for optional side air bags. DaimlerChrysler's minivans - the 2006 Dodge Grand Caravan and Chrysler Town & Country - improved from the worst score to the second-highest on a four-tier scale (poor, marginal, acceptable and good) when the air bags were included. The air bag option costs an additional $595. GM's four minivan models built on the same platform - the 2006 Chevrolet Uplander, Buick Terraza, Pontiac Montana SV6 and Saturn Relay - showed minor improvements when the side air bags were included, moving up one notch, to marginal.