The network performance model (NPM) was developed for Highways England by Risk Solutions. It is a software model that supports analysis of traffic performance on the strategic road network (SRN). It is used by the HA national intelligence unit (NIU) to support their analysis of network performance.
The nature of this model is that it can be calibrated to generate and store speed-density curves for road links of the Agency’s network. A stochastic process can then be used to derive expected performance characteristics of these links. The most frequent use of the model is to predict the likely characteristics of a road link’s performance, fed with recorded observed data such as traffic flows and journey times. This is particularly useful for informing the Agency about road performance characteristics that are infeasible to observe directly, such as which parts of the road were in congested flow at any time, given overall measurements of speed and flow.
Highways England uses this type of analysis to characterise the past performance of its roads, as well as to project scenarios about its expected future performance given various road investment strategies.