Advisory Intelligent Speed Assist (ISA) systems are those that integrate data about vehicle location with information about the speed limit of the current section of road and direction of travel, and which will alert the driver if the speed limit is exceeded.

We examine the potential of after-market portable navigation devices (e.g., smartphones and portable satellite navigation devices) to inform drivers about posted speed limits and to assist them to travel within the speed limits. Data sources include ISA effectiveness studies, manufacturer's product specifications, GNSS signal and device positioning theory, information related to performance characteristics and method of operation of GNSS signal emulators, digital speed limit maps provided with ISA-related software and human factors research associated with in-vehicle alerts.

At the time of the research project there were no standards or assessment protocols directly relevant to assessing after-market ISA devices therefore a draft assessment protocol was developed. It was found that it is feasible to assess and rate the performance of after-market ISA devices in an objective and repeatable manner. It is estimated that the better performing devices could reduce fatal and serious crashes by around 19% assuming widespread fleet penetration. An analysis of various implementations scenarios shows that a modest uptake in advisory ISA enabled PNDs is required to break even on implementation costs.