Geofencing, explained: zones that actually work

A geofence is a boundary drawn on a map around a real place: a depot, a customer's dock, a school gate, a project site. On its own it is just a shape, and it becomes useful the moment you attach a rule to it, such as tell me when this truck arrives, or warn me if anything moves here after dark.

Each vehicle already reports its position through a GPS tracker. The fleet software compares every new position with the zones you have drawn and decides whether the vehicle has crossed a boundary, is still inside, or has stayed too long.

Draw the wrong shape and you will miss real events or drown in false ones.

If you would describe the place by its boundary, draw a polygon. If you would describe it by the road, draw a corridor. If you would describe it by an address, a circle is usually enough.

• Polygon: a freehand outline that follows the real boundary, such as a depot wall or a warehouse and its yard. Use it when the place is irregular or sits beside a busy road you do not want included.
• Corridor: a band that follows a route, covering the road and a margin either side. Use it for fixed runs such as a school bus route, a milk collection round or a shuttle between two plants, where leaving the road is the event you care about.
• Circle or point-of-interest ring: a radius around a single point. Quick to set up across hundreds of customer addresses, and good enough where the site is compact and the surroundings are open.

The shape says where. The rule says what matters there. Most useful rules fall into a handful of families, and one zone can carry several at once.

Google's Android geofencing documentation advises that when alerts pile up from driving briefly past a zone, switching the trigger from entry to dwell means the alert is sent only once a vehicle has stopped inside for a set period.

• Entry and exit: the basic pair. Arrival at a customer site, departure from the depot, a bus leaving the school gate.
• Dwell: an alert when a vehicle stays inside longer than it should, such as a truck held at a dock well past its unloading slot.
• In-zone speed limits: a lower limit that applies only inside the zone, such as a campus, a plant yard or a school street.
• No-go zones: places vehicles should never be, such as an unapproved parking spot or a restricted area.
• Office-hours rules: the same zone behaving differently by time of day. Movement on a construction site at 11 am is work. At 2 am it deserves a phone call.
• Missed visits: a scheduled stop with no recorded arrival, flagged without anyone trawling through trips.

Every GPS position is an estimate. GPS.gov states that GPS-enabled smartphones are typically accurate to within a 4.9 metre radius under open sky, and that their accuracy worsens near buildings, bridges and trees, where signals are blocked or reflected off buildings or walls, an effect called multipath. A fitted tracker meets the same conditions.

The result is drift. A lorry parked tight against a depot wall can appear to wander in and out of the boundary, and each wobble reads as an exit followed by a re-entry. Under a flyover, inside a covered shed or at a basement dock, the tracker may lose its view of the sky altogether.

Location on a phone is a different animal. On most devices, Android's geofence service uses only network location for triggering rather than satellite positions, so Google recommends a minimum geofence radius of 100 to 150 metres, advises assuming Wi-Fi accuracy of about 50 metres, and warns that where Wi-Fi is unavailable, as in rural driving, the error can run from several hundred metres to several kilometres. That matters if any of your tracking comes from drivers' phones rather than fitted devices.

None of this makes geofencing unreliable. Zones must be designed with error in mind, and the software should filter out jitter before it decides a boundary has been crossed.

Most false alerts come from a few avoidable choices. Work through this list every time you draw a zone.

• Size for the error, not the drawing. Leave a margin beyond the real boundary so ordinary drift stays inside, and widen it wherever the sky is blocked.
• Keep the public road out. A zone that swallows a busy road turns every passing vehicle into an arrival. Trim polygons back to the gate line.
• Keep neighbours apart. Two customers on the same lane, or a depot next to a petrol pump, should not sit inside overlapping zones.
• Prefer dwell for arrivals that matter. A short minimum stay filters out drive-bys and wobble at the edge. Keep entry and exit triggers where the news has to be immediate, such as a no-go area or a depot gate at night.
• Name zones so a stranger understands them. Use one pattern, such as city, type and site: BLR Depot Peenya, HYD Customer Kukatpally Dock 2. An alert that says Zone 14 helps nobody at midnight.
• Group zones by purpose. Depots, customers, no-go areas and school zones need different rules and different recipients.
• Test before you trust. Replay a few weeks of real trips against a new zone and rule before alerts go live, then adjust the size or dwell time.
• Review every quarter. Customers move docks, sites expand and roads get widened, so last year's zone stops matching the ground.

Depots. Draw a polygon around the yard and gates, trimmed back from the main road. Alert on exits outside working hours, and on dwell when a vehicle that should be out on a run is still inside. Where vehicles and people share the yard, add an in-zone speed limit.

Customer sites. Circles suit compact addresses; polygons suit large campuses with separate gates. Arrival and departure times build an honest record of how long each drop really takes, and a scheduled stop with no arrival is a missed visit.

School streets. Make each stop and gate its own zone, so arrival, departure and waiting time are logged, and add a corridor along the route so a bus that strays is visible at once. Put a lower in-zone limit on the street itself, under whatever is posted there. The WHO's Streets for Life campaign, a recommendation to governments rather than Indian law, calls for a maximum of 30 km/h where vulnerable road users and vehicles mix in a frequent and planned manner, and the WHO's road traffic injuries fact sheet notes that every 1% increase in mean speed produces a 4% increase in fatal crash risk.

Construction sites. Outline each project boundary as a polygon and set rules that follow that site's working hours, so night-time movement stands out. Mark nearby areas where machines have no business as no-go zones, and use dwell alerts to find equipment idle while another site waits for it.

An in-zone limit targets the violation recorded most often in India's official crash statistics. In Road Accidents in India 2024, the Ministry of Road Transport and Highways records over-speeding as the violation behind 70.7% of road accidents, 70.3% of deaths and 70.9% of injuries. These are violations attributed by the reporting police, not established causes.

The legal limit on a road, though, is not yours to set. Section 112 of the Motor Vehicles Act, 1988 lets a State Government, or an authority it empowers, fix maximum and minimum speeds for a class of vehicle, an area or a stretch of road, by notification in the Official Gazette and by putting up traffic signs. The Central Government may fix a maximum for a class of vehicle by notification, and a state limit can never exceed it. Limits therefore differ from state to state and street to street.

An in-zone limit in fleet software is a management tool. It holds drivers to your own standard, which may sit below the posted limit but never above it. This guide is general guidance, not legal advice. Confirm the limits that apply to your vehicles, and the ceiling for your vehicle class, with your state transport department or RTO, especially for school buses and other passenger vehicles.