Urban Transportation and Logistics

68 Russell G. Thompson

application of GPS. Data captured from GPS devices can be used to

estimate energy expenditure from walking and cycling since the speed

and duration of movement can be determined.

However, there are a number of problems related to the application

of GPS to estimate the levels of physical activity from transport—such

as determining the mode and purpose of the trip as well as some loca-

tions that are not recorded due to weak signals. GPS data do not indicate

what transport mode a person has used. Techniques for automatically

determining the mode of transport are the focus of ongoing research.

The purpose of the trip or the activity undertaken at the end of the trip

is also not recorded by GPS. This limits the understa