How does black box or telematics car insurance work?
It prices your premium partly on how you actually drive, measured directly, rather than only on statistical proxies such as age, postcode and occupation.
How the data is collected:
A fitted black box, professionally installed and wired in.
A self-install plug-in device into the car's diagnostic port.
A smartphone app, now the most common, using the phone's sensors.
Built-in connected car data, where the manufacturer's telematics feed the insurer directly.
What is typically measured:
Speed, relative to the limit for the road you are on.
Acceleration and braking, particularly harsh events.
Cornering forces.
Time of day. Night driving — especially late weekend nights — carries much higher risk and is weighted accordingly.
Mileage, which is one of the strongest predictors of claims.
Journey type, since motorway miles are safer per mile than urban ones.
Phone handling in app-based schemes.
How it affects price: an upfront discount, then adjustments — some policies refund or discount at renewal, some adjust monthly, and some apply a curfew with penalties or cancellation for breaches.
Who benefits most. Young drivers, for whom conventional pricing is punitive because it reflects their age group rather than them; low-mileage drivers, who subsidise heavy users under flat pricing; and careful drivers generally.
The genuine drawbacks:
Harsh braking is penalised even when it was correct. Stopping sharply to avoid a hazard scores badly, which frustrates people and can encourage worse habits.
Scoring is opaque, and thresholds are rarely published.
Privacy. The insurer holds detailed location and behaviour data. Check the policy on retention, sharing and what happens to data if you leave.
Cancellation risk. Some policies can be cancelled for persistent poor scores or curfew breaches, and a cancellation must be declared to future insurers — a meaningful consequence.
Worth asking before buying: how the score is calculated, whether anyone else driving the car is monitored, whether hard braking is contextualised, and what happens if the device fails.
General information, not advice.