A licence plate recognition system that opens barriers for authorised emergency and service vehicles without requiring them to slow down - while deterring unauthorised access to roads leading to the runway.
Changi Airport's airside service roads are the arteries that connect the airport operations complex to the runways. They exist for a narrow and defined set of users - emergency vehicles responding to runway incidents, and authorised service vehicles on legitimate operational tasks. The problem CAG needed to solve was not controlling known authorised users. It was preventing other vehicles from accidentally using the roads and inadvertently compromising runway safety - while ensuring that when an emergency vehicle needed to move, nothing delayed it. Securevision was approached to design and build an LPR-triggered barrier system that could recognise authorised vehicles from a distance, open the barrier without requiring them to slow down, and physically deter unauthorised access. Awarded in September 2021 and completed in December 2021.
| Client | Changi Airport Group (CAG) |
|---|---|
| Location | Changi Airport - airside service road network |
| Sector | Institution - Transport Infrastructure / Aviation |
| Project Type | New installation - LPR-triggered barriers for airside service road access control |
| Awarded | September 2021 |
| Completion | December 2021 |
| Scope | LPR cameras, barrier arms (breakaway type), control system - dual-lane configuration with cross-lane plate capture |
The access control requirement at Changi's airside service roads is unlike a car park or a gated estate. The users are not office workers stopping at a reader and waiting for the barrier to lift. They are fire engines, emergency response vehicles, and operational service vehicles - some travelling at speed in response to a runway incident, some large and heavy enough that a barrier arm that does not open in time becomes a genuine safety event rather than an inconvenience.
CAG had considered two alternatives before approaching Securevision. Long-range proximity readers using active RFID tags would allow vehicles to be recognised at distance without stopping, but require every authorised vehicle to carry a physical tag - a credential that can be lost, transferred, or misused. The tag also only works if it is fitted, functional, and present. IU (ERP) readers were also considered, but were out of stock with no confirmed availability timeline, and the range characteristics raised concerns about whether they could reliably trigger a barrier early enough for a fast-moving vehicle approaching from a specific angle.
When CAG approached Securevision, we visited the site to understand the geometry and operational reality before proposing a solution. What we found added five specific engineering challenges that would shape the entire design.
| Access Control Function | Before | Securevision Solution |
|---|---|---|
| Unauthorised Vehicle Deterrence | No physical barrier - service roads open to any vehicle that found them | Barrier arms physically block the road; only LPR-matched plates trigger opening |
| Authorised Vehicle Recognition | No recognition system - no way to distinguish authorised from unauthorised at speed | LPR cameras recognise authorised licence plates and trigger barrier opening without requiring the vehicle to stop or slow down |
| Emergency Vehicle Passage on Non-Open | No barrier - nothing to manage | Breakaway arms engineered to detach on impact - if a barrier does not open in time, the vehicle passes through without damage to itself or its convoy |
| Credential Risk | No credentials - but also no control | Plate-based recognition - no physical tag to lose, transfer, or misuse. The vehicle is the credential. |
| Two-Lane Coverage | Not applicable | Cameras positioned to capture plates across both lanes simultaneously - emergency vehicles can drive down the centre and still be recognised |
Long-range RFID and IU readers both require the vehicle to carry something. That something has to be issued, fitted, maintained, and controlled. On an airport service road used by emergency vehicles from multiple agencies - airport fire services, ground handling, maintenance contractors - managing a tag-based credential system across a diverse fleet with multiple operators is a meaningful administrative and security burden. A tag that exists outside the vehicle can be removed, lent to an unauthorised vehicle, or simply not fitted in time for an emergency deployment.
Licence plate recognition removes the credential from the fleet and puts it on the vehicle itself. The plate is permanent, visible at distance, and cannot be casually transferred. The LPR camera reads it without any action required by the driver - the vehicle simply approaches and, if the plate is on the authorised list, the barrier opens. The approach is faster, more reliable in an emergency context, and easier to administer than any tag-based alternative.
The engineering decision that followed from choosing LPR was about camera placement and barrier specification. A standard LPR deployment assumes vehicles approach in a defined lane, at a moderate speed, with the plate at a standard height and position. None of those assumptions held at the CAG service roads. Five distinct challenges shaped every decision that came after.
Site visits before any specification work revealed the five constraints that would drive the entire design. Each had to be solved before the system could be commissioned. None could be resolved off a standard LPR specification sheet.
Unlike cars where the plate is at a consistent position and height, emergency vehicles mount plates differently - left, right, centre, and at heights of up to one metre or more on fire engines and heavy response vehicles. Camera height, angle, and field of view had to be chosen to capture plates across the full range of positions found in the authorised fleet.
The service roads are two lanes, each over six metres wide. In an emergency, vehicles may drive down the centre of the road rather than keeping to either lane. Cameras had to be positioned and configured to capture a readable plate across the full width of both lanes simultaneously - not just one lane at a time.
If a barrier does not open in time - a system lag, a plate that was not added to the whitelist, a recognition failure - an emergency vehicle must be able to pass through without causing damage to itself, the vehicle behind it, or the barrier mechanism. Breakaway arms are engineered with a clasp mechanism that allows the arm to detach when struck, absorbing the impact and allowing the arm to be refitted afterwards. This was a mandatory specification for an emergency vehicle application.
A breakaway arm is attached only at the clasp mechanism. When raised and exposed to wind - an issue on any exposed road, and particularly at an airport site - the arm can swing significantly. This affected how we specified the arm length, the clasp weight, and the raise speed so that the arm was stable in raised position without compromising the breakaway function when needed.
Several service road entry points are at T-junctions where vehicles approach from a sharp turn. At the angle of approach, a plate facing slightly away from the camera can be unreadable - even at moderate speeds. Camera placement had to be selected specifically for the geometry of each junction, not applied from a standard template, to ensure the plate was readable before the vehicle reached the barrier.
All installation work on the airside required Changi Airport clearance and an escort at all times. Any work affecting the service roads required the corresponding runway to be closed and flights redirected. A typical LPR-and-barrier installation takes three days at most. This project required clearance coordination, runway scheduling, and careful phasing to work within the operational windows CAG could make available.
Commissioning required real emergency vehicles to approach the barriers at operational speeds in the darkest conditions available - to test both the plate recognition performance and the barrier response time when visibility was at its lowest. Testing was arranged late at night specifically to replicate the most demanding conditions the system would face in a real emergency.
LPR cameras that read across both lanes at approach speed, breakaway barrier arms that yield if they do not open in time, and a commissioning process that tested the system with real emergency vehicles in the most demanding conditions available.
LPR cameras positioned and angled to capture licence plates across the full width of both lanes simultaneously, at the range and angle of approach specific to each service road entry point. Camera height and field of view were specified around the plate positions of the actual vehicles in the authorised fleet - including fire engines and emergency response vehicles with elevated plate mounting. Junction geometry was assessed on site and camera positions chosen to ensure the plate was readable before the vehicle reached the barrier.
Vehicle Access & LPR →Barrier arms specified with a breakaway clasp mechanism that allows the arm to detach when struck by a vehicle. If the system does not open in time - for any reason - the approaching emergency vehicle can pass through without damage to itself, its convoy, or the barrier mechanism. The arm detaches, absorbs the impact, and can be refitted after the event. Arm length and clasp weight were chosen to balance stability in raised position under wind load against the breakaway force threshold required for safe passage.
Vehicle Access & LPR →Authorised plates are held on a managed whitelist in the LPR control system. When a recognised plate approaches, the corresponding barrier opens before the vehicle reaches it - no stopping, no slowing, no driver action required. Unrecognised plates leave the barrier down, providing the deterrent function CAG required for vehicles that may accidentally approach the service road without authorisation.
Platform & Management →LPR cameras and breakaway barrier arms at the airside service road entry points, configured for dual-lane plate capture across the authorised vehicle fleet including fire engines and emergency response vehicles.
LPR Cameras: Hikvision LPR cameras at each service road entry point.
Barrier Arms: Breakaway barrier arms at each controlled entry point.
LPR Control System: Plate whitelist management and barrier trigger logic.
Plate-based recognition eliminated the need for active RFID tags or IU readers across a diverse fleet of emergency and service vehicles from multiple operators. The vehicle is the credential - permanent, visible, and impossible to transfer casually.
Breakaway arms mean a non-response event - whatever the cause - never stops an emergency vehicle. The arm yields, the vehicle passes, and the arm is refitted afterwards. Safety is not contingent on system uptime.
Late-night testing with real emergency vehicles at operational speeds in the lowest-visibility conditions confirmed recognition performance and barrier response before the system was handed over. CAG received a commissioned system, not a system waiting to be tested in operation.
A car park barrier is a friction point. You want a little friction - enough to make people stop and present a credential. An airside service road barrier is the opposite. You want zero friction for the vehicles that are supposed to be there, and absolute deterrence for the ones that are not. Those two requirements pull in opposite directions, and the only way to resolve them is to make the recognition fast enough and wide enough that authorised vehicles never experience the barrier at all - and to specify an arm that yields if the recognition fails, because in an emergency, the alternative is unacceptable. LPR got us the recognition we needed. The breakaway arm got us the safety we needed. The site visits got us the camera positions that made both work.
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