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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, r_{i} is the latitude and longitude coordinates of location i, n_{i} 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 r_{cm} 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. |