License Plate Recognition in Snow: Tackling Winter Challenges

Snow can make life tough for License Plate Recognition (LPR) systems, especially when it’s piling up on plates or messing with camera visibility. Whether you’re running a parking lot, managing a toll road, or keeping a university campus secure, winter’s challenges can "throw a wrench" in your operations.

The good news? Modern LPR tech has stepped up to handle snow, keeping things running smoothly. This article breaks down what makes snow such a pain for LPR, how today’s systems deal with it, and some practical tips for parking integrators, LPR users, and institutions to stay on top of winter conditions.

What Makes Snow a Problem for LPR

Snowy weather hits LPR systems with a few big hurdles:

• Plates Get Covered: Snow can pile up on license plates, obscuring letters and numbers, especially after a big storm or if a car has been parked for a while.
• Visibility Takes a Hit: Falling snow, fog, or weak winter light makes images blurry, so cameras struggle to get a clear shot.
• Lenses Get Blocked: Snow or ice sticking to camera lenses can disrupt captures, introducing distortion.
• Glare Issues: Snow’s reflective nature can cause glare in certain lighting, throwing cameras off their game.

These problems are a headache for parking integrators setting up access control, universities handling campus parking, or toll operators needing accurate reads for billing. A missed plate because of snow can mean errors, delays, or security issues, so you need an LPR system that’s ready for winter.

Real-World Testing in Icelandic Conditions

To better understand LPR performance in winter, real-world tests were conducted in Iceland, known for it's extreme weather conditions—snow, limited daylight, and cold winds.

The test involved 88 records and yielded a 99% overall performance rate using a dual-camera setup:

• Only 1 record (1%) was a complete miss, failing to read both front and rear plates.
• 14 records (15.9%) had at least one missed plate (either front or rear).
• 4 records (4.5%) were unrecognizable due to non-visible plates (damaged, frosted, or non-reflective)—conditions beyond the reach of software correction.

Lane Geometry and Visibility Challenges

It was noted that wide lane configurations reduced plate visibility, particularly during snow coverage. The extended field of view lowered detection accuracy, emphasizing the need for strategic camera alignment and possible lane narrowing where applicable.

System Enhancements and Adaptations

• Trajectory Verification: Plate read consistency was validated through trajectory tracking.
• Camera Maintenance: Regular upkeep was critical to ensure lens clarity amid snow and debris.
• Lighting Improvements: Firmware updates mitigated issues with extreme lighting (under- or overexposure), ensuring adaptive lighting could handle reflective snow and low-light conditions effectively.
• Traffic Mode Adaptation: In the Iceland deployment, the system was switched from Access Control to Urban Free Flow mode, accommodating traffic patterns where vehicles do not stop at entry/exit points.
• Plate Size Optimization: Optimal plate image sizing was achieved at 120–150 pixels, striking a balance between field coverage and recognition fidelity

Additional Technical Considerations:

• Network Quality: Stability of data transfer and real-time sync remained a factor to monitor in remote environments.
• Environmental Limitations: Some visibility challenges (e.g., frosted or damaged plates) cannot be fully addressed by software—highlighting the role of physical infrastructure and maintenance.

How Modern LPR Takes on Snow

Today’s LPR systems are built to handle snow like a champ, thanks to some smart tech upgrades. Deep learning and advanced image processing let these systems keep working even when snow’s causing trouble. Here’s what’s making the difference:

• Deep Learning: These systems can read plates that are partly covered, angled, or shot in low visibility, pushing through snow’s challenges.
• Image Denoising: This clears out the noise from falling snow, making images sharper for better reads.
• Contrast Boost: Enhancing contrast in dim or snowy conditions keeps plates clear.
• Infrared Lighting: Infrared (IR) cuts through snow and fog, giving clean captures day or night.

These features make modern LPR systems a solid choice for parking lots, toll roads, and campuses, ensuring you get reliable reads even in rough winter weather.

Tips to Keep LPR Running in Snow

Here’s some straightforward advice for integrators, users, and institutions to make sure your LPR system stays solid in snowy conditions:

• Go for Weather-Tested Systems: Pick LPR solutions that have been put through their paces in snow and other tough conditions. Ask vendors for proof of winter performance.
• Get Tough Hardware: Choose cameras with high IP ratings (like IP66 or IP67) to stand up to snow, ice, and cold. Infrared is a must for low-light or foggy situations.
• Place Cameras Right: Set cameras at entry/exit points or lanes to nail clear plate shots. Angle them to keep snow from piling up on lenses.
• Use Dual Cameras: In places needing both plates, dual cameras give you a backup. Linked systems, like Survision’s, boost accuracy by picking the best image.
• Stay on Maintenance: Check lenses regularly to clear off snow or ice. Heated lens covers can stop buildup before it starts, keeping your cameras crystal clear. Survision Guard is a tool that monitors your cameras 24/7 to ensure they’re always working optimally. If something happens, we send notifications ASAP to eliminate unnecessary downtime, so your system stays online even in the worst storms.

These steps keep LPR systems reliable, whether you’re an integrator rolling out a big project, a university managing parking, or a toll operator dealing with heavy traffic.

Snow doesn’t have to stop LPR in its tracks. With deep learning, infrared lighting, and tricks like image denoising, modern LPR systems are ready to tackle winter challenges, keeping parking lots, toll roads, and campuses humming along. In places requiring front and rear plates, dual cameras, especially with linked communication like Survision’s, make sure you don’t miss a read. By choosing systems tested for tough weather, setting up cameras smartly, and keeping up with maintenance, parking integrators, LPR users, and universities can stay ahead of the snow. 

Snowy Case Studies

Quebec Rouyn-Noranda Airport

One of the most northern airports in the world!

Town of Hampstead

Platenforce Mobile LPR Parking Enforcement solution helped employees to maximize efficiency

Medstar Medical Center at Maryland

Amano McGann and Survision provided a solution to manage monthly parkers and transients.