Induction loop and traffic light at the bollard: what safety technology does a commercial entrance need?

A pneumatically retractable V4A stainless-steel bollard in its standard version weighs around 160 kg, rises in 3 to 10 seconds and pushes upwards with a force of about 450 kg as it does so. At a private driveway with two users that is uncritical – everyone knows when the bollard is moving. At a company entrance with suppliers, visitors and staff travelling in both directions, however, the system itself has to know where a vehicle is at any given moment. This article explains from the manufacturer's perspective which safety technology ensures that a bollard never rises beneath a vehicle, which component does which job and when a traffic light is needed. It belongs to the topic area Access management for businesses and property; how to clarify the operating procedure of your entrance beforehand is described in the article Planning access control for company premises properly.

Why does a commercial bollard system need safety technology at all?

Because at a commercial entrance it is no longer a person but the system that decides when the bollard rises – and to do that it has to know whether the passage is clear. With a radio control, the driver presses the button, the bollard lowers, the driver passes through and presses again, or the bollard rises after a set time. That works as long as the same person controls both ends of the process. As soon as a supplier rolls through behind a member of staff, a visitor stops on the bollard to ask for directions, or two handheld transmitters are pressed at the same time, that control has lost its basis. The traffic control unit catches precisely these operating errors: repeated pressing, unsynchronised remote controls and a premature rise while the passage is still occupied.

Then there is visibility. A lowered bollard sits flush with the paving – that is its advantage over a barrier arm or gate, but also the reason why a driver unfamiliar with the site cannot tell, without a signal, whether the entrance is currently closed or about to close. The reference Delivery van rams bollard shows the case in which a driver with his eyes on his smartphone drove head-on into a raised bollard: bumper off, front end shifted, the bollard without a dent. That case is one of the reasons why, at commercial entrances, we count the LED ring and traffic light as safety technology rather than as optional extras.

How does the system prevent a bollard from rising beneath a vehicle?

By means of a safety loop immediately at the bollard: as long as a vehicle is standing over this induction loop, the control unit does not release the command to rise – regardless of whether a schedule, a handheld transmitter or the number-plate camera triggers it. Only when the loop reports clear again does the traffic control unit switch the traffic light to red and let the bollard rise. In the product logic of our traffic control unit this means: the bollard stays down until the vehicle has passed through completely, and the entire sequence is monitored. The fact that there is no electronics in the bollard itself is not a drawback but by design – the monitoring runs in the control cabinet, while all that sits in the ground is the stainless-steel cylinder, moved by compressed air at 8 to 10 bar.

That is how we solved it in a Berlin residential complex whose passage to the residents' parking spaces was regularly blocked by supermarket customers: two standard bollards of 160 kg each secure the covered passage. Residents open via radio transmitter, and the bollards lower as they approach. From the inside, an exit loop detects every vehicle and lowers the bollards automatically – visitors do not have to operate anything. An additional loop prevents a bollard from rising while a vehicle is standing over it; after the vehicle has passed through, the bollards rise again within a few seconds. The project is described in the reference Supermarket opposite: securing the parking spaces of a residential complex.

Which induction loops are there – and where are they laid?

A bollard system needs two loop functions: the safety loop at the bollard and the exit loop on the inside; with two loops one behind the other, the loop module of the traffic control unit also detects the direction of travel. An induction loop is nothing more than several turns of cable in the road surface through which a weak alternating current flows; when a mass of metal passes over it, the magnetic field changes and the loop module reports "vehicle". Pedestrians, leaves or snow do not trigger it – which sets it apart from a light barrier, which reports every interruption of the beam and therefore trips unnecessarily often at entrances with pedestrian and cycle traffic. That is why our systems work with induction loops; light barriers are not part of our product range.

Loop	Position	Task	What happens when it is occupied
Safety loop	immediately at the bollard, in the passage area	detect a vehicle over the bollard	rising is blocked until the loop is clear
Exit loop	inside, ahead of the bollard in the direction of travel	detect an exiting vehicle	bollard lowers automatically, no operation needed
Two loops one behind the other	inside and outside	determine the direction of travel	control unit distinguishes entry from exit, e.g. for the traffic-light logic

The loops are best laid before paving, together with the bollard's cable and hose bundle; cutting them into asphalt or concrete afterwards is possible but more involved. Practical values from our installations: the loop lies about half a metre in front of the bollard, the feeder cable is twisted at around 20 turns per metre, the standard length to the control cabinet is 15 m, and beyond that we use outdoor network cable up to a maximum of 50 m. The loop module with 2 × 50 m of loop cable is included with the traffic control unit; that is why there is no separate loop item in the shop. How the trench and pit are prepared is covered in the article Installing a retractable bollard.

When is a traffic-light column needed – and what does it show?

A traffic light is needed as soon as vehicles can meet on a single-lane entrance or the driver cannot see the bollard in time – behind a bend, a gateway or in low sun, for instance. It answers the one question for the driver that the flush-retracted bollard cannot: may I drive now? Green means the bollard is down and the passage is clear; red means closed or about to close – after the vehicle has passed through, the traffic control unit switches to red first and only then lets the bollard rise.

Our stainless-steel traffic-light column is 3.00 m long, of which 2.20 m stands visible above ground and about 80 cm sits in the foundation. It is made of 3 mm satin-finish stainless steel and carries either two red LEDs (€1,350) or two red and two green LEDs (€1,450), each rated at 15 W. The four-LED version is intended for opposing-signal control: the column is visible from both directions and shows entering and exiting vehicles their own phase. It is driven by the traffic control unit, or on request via GSM, induction loop or radio. We define the specific phase durations for each system; there is no amber phase as in road traffic, because the bollard does not start moving while the safety loop is occupied.

What do the LED ring and flashing light add?

The LED light ring in the bollard head turns the bollard itself into a signal: it runs on 12 V, lights up in any colour you choose and can be switched between steady light, rotating light, running light and flashing light via a Bluetooth app. Red for closed and green for clear is the usual choice, and at night the red ring is visible from a long way off. It does not replace the traffic light, because it is only clearly visible once the bollard is already up – but it is included with every standard bollard and, for entrances without oncoming traffic, is often the only signal that is needed. The traffic control unit additionally has its own outputs for a flashing light, LED warning lights, sounders and the 12 V lighting control for the bollard illumination, so that a flashing light can be switched on during the movement, for example.

In our reference project at a Lidl car park, three retrofitted bollards in front of the sliding gate are fitted with all-round LED lighting so that customers can make them out at dusk; the bollards rise before deliveries, creating a turning area for the lorry, and then retract flush again afterwards.

Which control unit links loops, traffic light and bollards?

The traffic control unit with Loxone Miniserver for €2,150 is the hub where all the safety components come together – a radio control for €245 cannot do this; it is expressly not designed for induction loops or radar sensors. The DIN-rail housing of the traffic control unit contains a pre-configured Loxone Miniserver Gen 2, the loop module with direction detection and 2 × 50 m of loop cable, connections for a traffic light (red/green), LED warning lights, flashing light, sounder, switches and push-buttons, fingerprint reader, number-plate recognition and a fire-brigade signal, plus an 868 MHz radio receiver with external aerial and 5 m of cable for a range of up to 100 m. It is powered from 230 V, with the 12 V and 24 V power supplies integrated; the housing measures about 30 × 35 × 15 cm and weighs around 5 kg.

Component	Role in the safety chain	Price incl. VAT (as at 09/2026)	Worthwhile from
Traffic control unit with Loxone Miniserver	Monitors the sequence, keeps the bollard down until the vehicle has passed through completely, switches traffic light and lighting	€2,150	more than 10 passages/day or changing users
Loop module with 2 × 50 m of cable	Safety loop, exit loop, direction detection	included with the traffic control unit	every system with automatic rising
Stainless-steel traffic-light column	Unambiguous drive signal, coordinating two-way traffic	€1,350 (red) / €1,450 (red + green)	single-lane entrance, restricted visibility
LED light ring in the bollard head	Makes the bollard visible in the dark, shows its status	included with the standard bollard	every entrance
Number-plate recognition	Checks authorisation without a handheld transmitter, signals the traffic control unit	€1,950	many changing but registered vehicles
Compact radio control	Opening by handheld transmitter, without loops	€245 (handheld transmitter €29.50)	up to 10 passages/day with regular users

The traffic control unit communicates with existing building technology and control rooms via LAN, KNX, web and app; by remote access we can read out faults in real time, change schedules and install updates without travelling to site. A complete overview of the operating methods is given in the article Bollard control: radio, GSM, number-plate recognition or smart home?; what needs to be observed under data-protection law for number-plate recognition is explained in the article Number-plate recognition at the entrance and the GDPR. For the installation of the traffic control unit, loops, traffic light and camera we allow one working day plus the network connection; the 230 V connection is a job for a qualified electrician.

How does a secured passage work step by step?

A passage through a system with traffic control unit, loops and traffic light runs in six steps, of which the driver notices only two: the opening and the green signal.

1. Idle state: the bollard is raised, the traffic light shows red, the LED ring lights up red.
2. Trigger: a handheld transmitter, a call to the GSM module, a match from the number-plate camera, a schedule or – on exit – the exit loop sends the command to the traffic control unit.
3. Lowering: the bollard travels down in the set rise time of 3 to 10 seconds; as soon as it is down, the traffic light switches to green.
4. Passage: the vehicle rolls over the safety loop. As long as it is occupied, no command can make the bollard rise – not a second handheld transmitter and not an expiring schedule either.
5. Release: the loop reports clear and the control unit switches the traffic light to red.
6. Rising: the bollard rises and locks mechanically at the top; the compressor runs on for about 30 seconds and switches off.

With two-way traffic, direction detection comes into play: if the loop module detects an exiting vehicle, the control unit can hold the traffic light on the entry side at red until the passage is clear again. The exit needs no authorisation – whoever is inside may leave, so the loop alone is sufficient here.

What happens in a power cut, a compressor failure or a fire-brigade call-out?

The operator sets the behaviour in a power cut in advance at the valve: either the bollard lowers and opens the entrance, or it stays up and keeps it closed. Which setting is right depends on what is being protected – a fire-brigade access route is usually set to "open", theft protection to "closed". A bollard locked in the raised position cannot be pushed down and stays up even if the air line is severed; it is unlocked with a short burst of compressed air and can be raised at any time as soon as voltage is present at the valve and 8 to 10 bar is available. Because there is no electronics, no battery and no limit switch in the bollard, nothing needs to be re-taught after an outage.

If the compressor fails, a raised bollard with height lock stays locked in the up position; the compressor is swapped via quick-release coupling in a few minutes, a replacement costs around €180 to €195 and arrives by express delivery. For entrances that must never stand still we recommend two to three compressors in synchronised operation, and anyone with a workshop with a compressed-air network can supply the bollard from it in the meantime. For the emergency services, the traffic control unit has its own connection for a fire-brigade signal and can be linked to control rooms – at the Große Freiheit in Hamburg's St. Pauli district, the Davidwache police station controls six bollards together or individually so that emergency vehicles can always get through. More on failure strategies can be found in the FAQ on retractable bollards.

What does this look like at real entrances?

Three of our projects show three levels of safety technology. The Berlin residential complex works with radio for entry, an exit loop and a safety loop – without a traffic light, because the passage is easy to oversee. At Hamburg City Hall, a Loxone Miniserver handles the control and monitoring of the pneumatic bollards, which are lowered at the push of a button; the bollard head bears the milled Hamburg coat of arms, and the V4A material withstands road salt and graffiti. At the Große Freiheit, six bollards protect the nightlife strip every day from 8 pm to 6 am, while during the day they are lowered for deliveries and tradespeople; every rise locks mechanically, and the lock is only released by a controlled lowering from the control room.

The key points in three sentences

A commercial bollard system is safe when an induction loop directly at the bollard blocks it from rising while a vehicle is standing over it, an exit loop opens the exit without any operation, and the traffic control unit only lets the bollard rise again once the vehicle has passed through completely and the traffic light has switched to red – all monitored in the control cabinet, while all that sits in the ground is the stainless-steel cylinder of the pneumatically retractable V4A stainless-steel bollard. The traffic control unit with Loxone Miniserver from Braun Antriebe costs €2,150 including a loop module with 2 × 50 m of cable, the stainless-steel traffic-light column €1,350 with red or €1,450 with red and green, and they are the right choice from more than ten passages a day or with changing users, whereas for up to ten passages with regular users the radio control for €245 is sufficient. Braun Antriebe manufactures bollards and control technology in Seevetal near Hamburg, has equipped entrances at a Berlin residential complex, Hamburg City Hall and the Große Freiheit with precisely this safety chain and supports the traffic control unit by remote access on request; the prices in this article are our list prices from September 2026.

You will find all bollards, control units, traffic-light columns and compressors in the V4A stainless-steel bollard collection; which bollard withstands which impact is explained on the page Security bollards.