Answers to the most common questions about GPS speed camera detectors, sat navs with speed camera alerts, and radar and laser detectors. If you are choosing a device for the first time, the speed camera detector buying guide is a good place to start.
Speed Camera Detector FAQ's
Are speed camera detectors legal in the UK?
GPS-based speed camera detectors are fully legal in the UK. They work by alerting drivers to the known locations of speed cameras held in a database and do not detect, interfere with or jam any camera or enforcement equipment in any way. The legal position has been settled since 2004, when the Department for Transport explicitly excluded GPS warning devices from any proposed restrictions during the Road Safety Bill process.
Radar and laser detectors are also currently legal to own and use in the UK. They detect signals passively and do not interfere with or block camera equipment.
Speed camera jammers - devices that actively emit a signal intended to disrupt or block the operation of a speed camera or radar gun - are illegal in the UK. Using or possessing a jammer is a criminal offence. GPS detectors and radar or laser detectors are not jammers and are treated entirely differently under the law.
Read the full speed camera detector legal guide
What is the difference between a speed camera detector and a speed camera jammer?
The key distinction is whether the device emits a signal or merely receives one. A speed camera detector - whether GPS, radar or laser based - is a passive device. A GPS detector reads its own position from satellite signals and cross-references it against a database of known camera locations. A radar detector listens for radio signals emitted by speed cameras and radar guns. A laser detector listens for the infrared pulses emitted by laser speed guns. None of these devices transmits anything or interacts with the camera equipment in any way.
A speed camera jammer is the opposite. It actively broadcasts a signal specifically designed to overwhelm or confuse a radar gun or speed camera, preventing it from taking an accurate reading. The intent is to block enforcement, not simply to warn the driver. This is why jammers are illegal - they constitute an active attempt to defeat law enforcement equipment, which is a criminal offence in the UK.
If you see a product described as a "detector" that also claims to prevent cameras from reading your speed, it is either a jammer or a fraudulent claim. Legitimate GPS, radar and laser detectors make no such claim and do not function that way.
Will a speed camera detector warn me about mobile camera vans?
A GPS-based detector or sat nav with a speed camera database includes known mobile camera hotspot locations - sites where mobile enforcement is regularly deployed. As you approach one of these locations, the device alerts you to be aware. The database is built from historical records of where mobile cameras have been operated.
However, the GPS alert tells you the zone, not whether a camera is actually present on that day. Mobile camera operators do not operate on a fixed schedule, and the same site may or may not be manned when you pass through it. The alert is a prompt to check your speed in a zone where enforcement is known to occur, not a live confirmation that a camera is active.
A radar or laser detector can in principle detect an active radar or laser gun at a mobile site - but the warning time may be very short, particularly for laser. For mobile sites on faster roads, a GPS alert gives useful advance distance while a radar or laser alert may come with little time to react. Many drivers use a GPS device as the primary warning and regard radar or laser detection as a supplementary layer rather than a replacement.
Can a detector tell me if I have actually been caught by a camera?
No speed camera detector can tell you whether a fixed camera has captured your vehicle. A GPS detector warns you to the location of the camera - it does not monitor whether the camera is active, whether it has triggered, or whether your speed exceeded the threshold. The device has no way of knowing what the camera has or has not recorded.
Many people assume that the absence of a flash means they have not been caught. This was a reasonable assumption with older Gatso cameras, which used a highly visible flash. However, many modern camera systems record without any visible indication at all - no flash, no noise, nothing that would be apparent to the driver. The absence of an obvious sign does not mean no capture has occurred.
The only reliable confirmation that a prosecution is being pursued is a Notice of Intended Prosecution (NIP) arriving in the post, typically within 14 days of the offence. If no NIP arrives within that window, no prosecution is being brought for that incident.
Do any detectors show the speed limit on all roads, not just at cameras?
Yes. Many current GPS-based detectors and sat navs include a speed limit database covering all road types across the UK, not just locations where a speed camera is recorded. The device shows the current road's speed limit continuously on screen as you drive, regardless of whether there is a camera nearby.
This is separate from the speed camera alert function. It works as a constant speed limit reminder - useful when driving in unfamiliar areas where the limit changes frequently or where signage may have been missed. Most current Garmin sat navs and the Snooper MY-SPEED PLUS include this as standard. For some devices, the speed limit database is included with the camera database subscription; for others it is a separate feature.
Will my detector work through a heat reflective windscreen?
Not reliably, without an external GPS antenna. A heat reflective windscreen - sometimes described by manufacturers as Comfort Glass or Thermally Insulated Glass - contains a very thin metallic coating designed to reflect solar infrared radiation and keep the cabin cooler. That same coating also blocks or significantly weakens GPS satellite signals, which travel at a similar frequency range.
A GPS device mounted inside a heat reflective windscreen may take much longer than usual to acquire a satellite fix, may lose the fix intermittently while driving, or in some cases may be unable to maintain a fix at all. A standard heated windscreen that uses fine filaments to demist the glass does not cause this problem - heated and heat reflective are different technologies.
Vehicles commonly fitted with heat reflective glass include certain models from Renault, Citroen and Peugeot, and some models from other European manufacturers. The windscreen is usually identifiable by a subtle blue or green tint and a small printed logo in the corner of the glass.
The solution is an external GPS antenna - a small passive receiver roughly the size of a matchbox that connects to the GPS device via a short cable. Positioned on the rear parcel shelf, on the dashboard near the edge of the glass, or on the vehicle exterior, it picks up the satellite signal directly and bypasses the coated windscreen entirely. Not all GPS devices include an external antenna socket, so check the specification of any device you are considering if you know your vehicle has heat reflective glass.
Read the full detector installation guide
Can I use a speed camera detector in a high-sided vehicle or van?
Yes, a GPS-based detector or sat nav works equally well in a van or high-sided vehicle. The alert is triggered by GPS position as you approach a recorded camera location - it is based on where you are on the road, not on whether you have a direct line of sight to the camera. Warning distance is typically 300 to 800 metres ahead of the camera location, depending on the device and the camera type in the database. This gives exactly the same advance notice to a van driver as to a car driver.
Radar and laser detection in a high-sided vehicle is a slightly different matter. A camera operator positioned at the roadside may be able to see the top of a high-sided vehicle approaching from further away than the radar or laser signal has reached the detection unit in the cab. This means the officer may already be preparing to take a reading before the detector has fired. GPS-based alerting removes this issue entirely, since the warning is based purely on position rather than on detecting the camera's own signal.
Can radar or laser detection warn me in time before I am caught?
For radar detection, the answer is usually yes. A radar speed camera or handheld radar gun emits a conical signal that scatters ahead of the target vehicle, and a detector can pick up this scattered signal at considerable range - often several hundred metres. This typically gives useful advance warning, particularly on faster roads where the approach speed is higher.
For laser detection, the timing is considerably less reliable. A laser gun fires a narrow, focused beam aimed at a specific vehicle. Because the beam is so narrow, there is very little scatter for a detector to pick up before the beam itself strikes the vehicle. In practice, by the time a laser detector triggers an alert, the laser may have already completed a speed measurement. The alert confirms the vehicle has been targeted, but may not provide any meaningful warning window.
This is a fundamental limitation of laser detection that is worth being clear about before buying a laser detector. A GPS database - which warns you to the location before you reach it - is a more reliable first line of defence against laser-equipped mobile enforcement, because it does not depend on detecting the device's signal at all. Radar detection provides a useful supplementary warning specifically for live Gatso cameras and active handheld radar guns.
Read the full guide to radar and laser detectors
Can I use a speed camera detector in the Republic of Ireland?
GPS-based speed camera detectors and sat navs with a speed camera database can be used legally in the Republic of Ireland. Many speed camera database subscriptions include ROI camera locations alongside UK coverage, so the same device that warns you on UK roads will also alert you to fixed and mobile camera sites in Ireland.
Radar and laser detectors are illegal in the Republic of Ireland. Possession of a radar or laser detector is an offence, regardless of whether the device is in use. If you have a combined GPS and radar or laser detector, the radar or laser function should not be used in the Republic of Ireland.
Before buying, check that the specific device or database subscription you are considering includes Republic of Ireland coverage - not all do. Some subscriptions cover Great Britain only.
Read the full European legal guide for speed camera detectors
Will a radar detector detect unmarked police cars?
Only in limited circumstances. A radar detector responds to any active radar signal on the frequencies it monitors. If an unmarked police car is using a radar gun that is actively emitting a signal, and that signal is within the detection range of the device, the detector will respond. In that narrow sense, yes, an active radar gun in an unmarked car is detectable.
However, police vehicles use other speed measurement methods that cannot be detected by any device. CCTV pacing - also known as following - involves an unmarked police car following a suspect vehicle at a constant distance for a measured section of road. The onboard camera records the odometer, the duration and the distance to establish the average speed over that section. No radar or laser is used at any point in this process. A radar detector has no way to detect this technique, because no signal is being emitted.
A GPS speed camera detector is similarly unable to detect any moving police vehicle, marked or unmarked - GPS-based alerting works from a static database of known locations, not from any signal originating from the vehicle.
If you have a question about speed camera detectors that is not answered here, use our contact page to submit it.
Last updated: May 2026.