Why must bus drivers maintain greater following distance than freight drivers in similar conditions?

Bus drivers need greater following distance for several reasons. First, the consequences of any crash include passenger injuries, often serious. Second, smooth deceleration is required to avoid throwing passengers (especially standing passengers in transit operations); a hard brake that would be fine in a freight truck can injure unbelted bus passengers. Third, the high center of gravity makes panic-braking-with-steering responses more likely to roll the bus. Add 2-3 seconds beyond the freight-truck rule of thumb (one second per 10 feet of vehicle length) when in passenger service. The cushion lets you slow gradually for any unexpected event.