# Alternating one-way ramp: Chronos traffic lights, loops and VIACONTROL — 3D demo | Stagnoli Accessories URL: https://www.stagnoliaccessories.com/en/use-cases/alternating-one-way-traffic Fonte: Stagnoli T.G. S.r.l. (Stagnoli Accessories), Lonato del Garda (BS), Italia Aggiornato: 2026-11-06 > How to regulate a single-lane car park ramp with Stagnoli products: two Chronos traffic lights, magnetic loops with DA035 detector and VIACONTROL control unit in priority, time or status mode. Interactive 3D traffic simulation. Use case · Private roads # Alternating one-way system One ramp, a single lane, cars going up and down. Two traffic lights and a control unit decide who goes, with no meetings halfway. Send cars, change mode, test the emergency. How it works ## Green to one, red to the other, never halfway. On a single-lane ramp the problem isn't who goes first: it's making sure two cars don't end up nose to nose in the middle. The clearance phase, all red while the ramp is occupied, is what prevents it. | Mode | How green starts | When to use it | Sensors | |---|---|---|---| | **F1 Priority** | At rest the F3 state applies. A car on the loop starts the cycle: TSG clearance (all red), TV green to the requesting side, TSG again, back to rest | Residential exits, garage ramps with irregular traffic | Loops, PRAP or photocells | | **F1 Time** | Fixed cycle TV1 → TSG → TV2 → TSG | Industrial driveways, building sites, constant traffic | Not needed | | **F1 Status** | Green stays on as long as its input is held | Emergencies, oversized loads, manual control from the gatehouse | Button or contact | | **F3 rest V1 R2** | S1 always green, S2 red until the S2 loop requests passage | Exit onto a public road: street traffic doesn't stop. One loop is enough, on the garage side | 1 loop (input of the traffic light red at rest) | | **F3 rest R1 R2** | Both red; green to the side whose loop detects a car | Residential ramps with similar traffic in both directions | 2 loops | | **IN3 alarm** | First the clearance time, then state F4 (default: flashing reds) | Fire protection, evacuation | Alarm contact | Layout ## Space to wait, space to exit. An alternating one-way system works if there is a two-lane area before and after the narrow section: one for those waiting for green, one for those who have just passed. - **Stop line and traffic light** on the waiting lane, to the right of approaching traffic. - **Magnetic loop only in the waiting lane**, under the stopped car: a car leaving in the other lane doesn't trigger it and doesn't create requests in the wrong direction. - **TSG clearance time** calculated on the ramp length: it must be enough for the last car that entered on green to leave the single lane. The kit ## What a ramp needs. ![Chronos CHR2LRV traffic lights](https://www.stagnoliaccessories.com/web/image/298337-d7c0f19c/Stagnoli%20%C2%B7%20chronos-alu.webp) ×2 ### Chronos CHR2LRV traffic lights One on each side. Runs on 24 V or 230 V with the same code. For tight spaces: ERA80. [Chronos](https://www.stagnoliaccessories.com/en/light-signalling/industrial-traffic-light-systems.md) ![VIACONTROL traffic light control unit](https://www.stagnoliaccessories.com/theme_stagnoli_accessories/static/src/img/viacontrol.webp) ×1 ### VIACONTROL control unit 2 traffic lights, 3 modes, 6-module DIN. For systems with several ramps: Saturno, up to 10 traffic lights. ![DA035 loop detector](https://www.stagnoliaccessories.com/theme_stagnoli_accessories/static/src/img/da035.webp) ×1 ### DA035 detector + 2 loops Two channels, one per loop, on DIN rail. Alternatively PRAP sensors. [Sensors](https://www.stagnoliaccessories.com/en/sliding-gates-safety/loop-detector.md) ![Apartment-block ramp with traffic light](https://www.stagnoliaccessories.com/theme_stagnoli_accessories/static/src/img/app-rampa-v2.webp) Calculate ### Cables and consumption Long 24 V line? Check the cross-section. And how much it costs to keep it on for a year. [Energy impact](https://www.stagnoliaccessories.com/en/docs/calculators/energy-impact?preset=sua) Frequently asked questions ## What property managers and installers ask us. **D: Are loops really necessary?** Only in priority mode, where green starts on request. In time mode the control unit alternates by itself. Instead of loops, PRAP microwave sensors or photocells can be used. **D: What happens if two cars arrive from both sides at once?** The control unit serves whoever has been waiting longest first, then the other side. Between the two greens there is always the clearance phase, with both lights red. **D: Which control unit should I choose?** For a ramp with two traffic lights, VIACONTROL or ACNSEM3L. For multi-storey garages with several ramps and space counting, Saturno, which manages up to 10 traffic lights with master/slave boards connected via RS485. **D: Can I power the traffic lights at 24 V from the gate control unit?** Yes, Chronos runs on 24 V ac/dc. If the ramp is long, check the voltage drop with the [calculator](https://www.stagnoliaccessories.com/en/docs/calculators/voltage-drop?v=24), or use a 230 V supply. ## Got a ramp to regulate? Send us the ramp length, type of access and available power supply: we'll propose traffic lights, control unit and sensors. [Contact us](https://www.stagnoliaccessories.com/en/contacts.md) [+39 030 9139511](tel:+390309139511)