The impact of Abnormal Loads on network performance

The HA aims to meet network performance targets under the Public Services Agreement (PSA), including the PSA1 value defined as average delay on the 10% most delayed journeys along a specified set of primary routes. Abnormal Indivisible Loads (AILs), which behave as moving bottlenecks, can cause considerable delay, and methods have been developed to model their effect. These methods have been extended to estimate their impact on the PSA value with the aim of estimating the benefit of various policy options.