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Table 1 Description of the GPS-based driving indicators

From: GPS driving: a digital biomarker for preclinical Alzheimer disease

Characteristics Indicator Abbreviation Description
Driving space Average trip distance TripDist The average distance travelled in each trip. TripDist is computed by taking the average of all the trips that a participant has made during the study period.
Total travelled distance TotalDist The total distance travelled during the study period.
Number of trips nTrips The total number of trips made during the study period. The trips are also placed into five subgroups: (1) trips with a distance smaller than 1 mi, (2) trips with a distance between 1 and 5 mi, (3) trips with a distance between 5 and 10 mi, (4) trips with a distance between 10 and 20 mi, and (4) trips with a distance of more than 20 mi.
Radius of gyration Rg Typical distance travelled by an individual, computed using [29]:
\( {r}_g=\sqrt{\frac{1}{N}\sum \limits_{i\epsilon L}{n}_i{\left({r}_i-{r}_{cm}\right)}^2} \)
where L is the set of destinations by the individual, ri is the latitude and longitude coordinates of location i, ni is the visitation frequency of location i, \( N=\sum \limits_{i\ \epsilon L}{n}_i \) is the total number of visits of the individual, and rcm is the center of mass of the visited destinations.
Entropy S The degree to which a participant’s trip destinations are random (i.e. unpredictable) in space and time [30]. S is assessed over the entire period of the study.
Number of night trips nNightTrip The average number of trips made after sunset.
Number of unique destinations nUniqDest The total number of distinct destinations that an individual visited during the entire study period.
Driving performance Number of hard brakes per mile nHardBrake The average number of events with a deceleration rate of above 8 miles per hour in 1 s per mile.
Number of sudden acceleration per mile nSuddenAcc The average number of events with an acceleration rate of above 8 miles per hour in 1 s per mile.
Overspeed OverV The average number of trips with a speed of 6 miles per hour above the posted speed limit.
Underspeed UnderV The average number of trips with a speed of 6 miles per hour below the posted speed limit.
Average speed avgV The average speed of trips.
Average acceleration avgA The average acceleration of trips.
Average jerk avgJ The average jerk of trips. Jerk is the rate of change of acceleration [31]; that is, more abrupt brake actions or accelerations lead to higher jerk values.