The Impact Score approach determines the relative impact of attributes on overall satisfaction, by
measuring customers' relative decreases in overall satisfaction, when a recent problem with an attribute
is reported. This makes sense because, within the delivery of quality service framework, the primary
way transit agencies can improve customers' overall satisfaction with service is to reduce customers'
problematic experience with those attributes which have the greatest negative impact on overall
satisfaction. These driver attributes can be identified and prioritized in a three-step process.