Finally, the third line of research, which has grown recently, deals with the use of GPS data of varying coverage levels that
provide a reliable source of information with great potential for speed monitoring. For example, Storey and Holtom (2003)
presented a United Kingdom application that uses historical data from different types of vehicles and concluded that GPS
speed measurements are more accurate than moving car observer measurements. Jiang (2001) studied the effect of road
work areas (on the Indiana freeway) on speed using a test vehicle equipped with a GPS. They estimated acceleration and
deceleration rates based on one-second time intervals. They affirmed that GPS data are more accurate than data obtained
using traffic counters. Greaves and Figliozzi (2008) used a GPS survey of commercial vehicles in Melbourne, Australia to obtain
profiles of truck speeds. Furthermore, Gurushinghe et al. (2002) reported the result of an empirical study made on a
probing field, which concluded that the accuracy of the data obtained using GPS technology was superior to that of the same
data obtained using conventional measurements.