Geofences in NEMT: how location boundaries mark arrivals and departures
A geofence is a virtual boundary, usually a circle around a GPS point, that lets software notice when a device enters, leaves, or lingers inside an area. In NEMT, a fence around a pickup or drop-off address can timestamp a van's arrival and departure. Phone location is imprecise, so Android's developer guidance puts the minimum radius at 100 to 150 meters.
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How a geofence works
A geofence has three parts: a latitude, a longitude, and a radius. Together they draw a circle on the map. Software on the driver’s phone watches for three events:
- Enter. The device crosses into the circle. In NEMT this usually means the van has reached the pickup or drop-off.
- Dwell. The device stays inside for a set time. Android’s guidance says a dwell trigger cuts the flood of alerts from devices that pop in and out of a fence, which suits vans that often pass a stop without pulling in.
- Exit. The device leaves the circle. With a rider aboard, that marks the departure.
Each stop on a manifest can get its own fence. Software can record the event as the arrival time, or use it to prompt the driver to tap Arrive so the tap becomes the record. Android allows up to 100 active geofences per app for each device user.
Accuracy limits
A geofence is only as precise as the location behind it, and phone location is rougher than most people assume:
| Condition | Typical accuracy |
|---|---|
| Smartphone GPS under open sky (GPS.gov) | About 4.9 meters (16 feet), worse near buildings, bridges, and trees |
| Wi-Fi available (Android) | Usually 20 to 50 meters |
| Indoor location available (Android) | As tight as 5 meters |
| Driving in rural areas without Wi-Fi (Android) | Several hundred meters to several kilometers |
Two more limits matter for trip times. On most Android devices, the geofence service uses network location only, not GPS, because it draws less power and works indoors. Alerts also lag: usually under two minutes, two to three minutes when background limits apply, and up to six after a device has been still for a long time.
For dispatch, that means a fence can fire a block early or a few minutes late. A hospital campus is the hard case: the address point may sit at one entrance while the rider waits at another. Treat a geofence event as one piece of evidence next to the driver’s own tap and the GPS trail, and check it before it decides whether a pickup was late or a rider was a no-show.
What brokers and states ask for
Programs want the location record, not a specific technology:
- New York made GPS compliance mandatory for Medicaid transportation providers on April 3, 2023. For each trip, the provider hands its broker the origin, the destination, and the full breadcrumb of coordinates between them. The state says it uses that data for program integrity, rider safety, policy planning, and fighting fraud. MAS, the statewide broker, requires every event on the trip to be logged in real time, either by hand or with a tool such as geofencing. If the GPS record disagrees with the invoice’s approved pickup point, drop-off point, or mileage, the trip cannot get the prior authorization its claim needs.
- MTM Health requires GPS data for all pickups and drop-offs, collected from the moment the driver leaves the depot. Its driver app asks the driver to tap Arrive before completing each stop, and warns that skipping the step can spoil the GPS record. Its 2026 Virginia handbook scores GPS compliance, with a target above 90 percent of trips digitally tracked.
A clean location trail also backs up the trip log and the loaded miles you bill. The documentation requirements guide lists the other records programs expect.
Handling location data
Location points tied to a rider are sensitive. HIPAA’s de-identification rule in 45 CFR 164.514 lists geographic units smaller than a state, including street addresses and their equivalent geocodes, among the identifiers. Keep trip trails inside the same access controls as the rest of the trip record. The HIPAA guide for NEMT covers the wider rules, and the guide to map apps for NEMT covers rider addresses in consumer navigation apps.
Drivers are tracked too. Android advises apps to explain clearly why they use location in the background. Starting collection at depot departure, as MTM Health does, ties tracking to the working day.
Seeing vehicles live
HealthRide’s live map shows every vehicle on one map in real time. Completed trips keep their times and GPS-recorded miles for later questions.
Frequently asked questions
- Is a geofence something the broker requires?
- Not by name. The programs covered here want GPS data and leave the method open. MAS, New York's statewide broker, wants every trip event logged as it happens, whether the driver enters it by hand or a tool such as geofencing captures it. MTM Health requires GPS data for every pickup and drop-off, from its own driver app or compatible GPS software.
- Why did the app mark a van as arrived when it was still down the street?
- Because the fence is wider than the curb. With a 100 to 150 meter radius, a van can enter the circle a block away, and Android alerts usually arrive within two minutes, sometimes up to six. Using a dwell rule, which waits until the device stays inside for a set time, cuts false arrivals from vans driving past.
- Is trip location data protected health information?
- Treat it that way. A rider's pickup address and the trail to a clinic reveal where they live and where they get care. HIPAA's de-identification standard lists street addresses and their equivalent geocodes among the identifiers that must be removed before health data counts as de-identified.
