RATP, Paris Saint-Lazare: 400 m² of glazing cleaned by drone in one night
Paris Saint-Lazare is one of the busiest stations in Europe. Its glass “lens” sits above live tracks and could not be cleaned without stopping trains or putting people at height. In October 2025, CleanAlta cleaned it by tethered drone, at night, in a single intervention.
In short: 400 m² of glazing above the tracks of Paris Saint-Lazare, cleaned in one night by a tethered drone with heated purified water, with no interruption to train traffic and nobody at height. RATP reports that the intervention time was divided by five compared with its usual method.
- ClientRATP
- SiteParis Saint-Lazare station
- DateOctober 2025
- Surface400 m² of glass
- DurationOne night
- Time saved÷5 (RATP figure)
The problem
The glass structure above the station tracks collects dust from the trains, city soot and rain marks. Cleaning it with the usual method meant several nights of work with technicians at height, each requiring a traffic interruption window. For an operator that runs trains almost around the clock, every night of work is a cost on its own.
What CleanAlta did
We prepared the job with RATP’s station management and safety teams: ground perimeter, electrical safety near the catenary, timing between the last and first trains, and the authorisation to fly in central Paris. On the night, a tethered drone under 25 kg sprayed heated purified water at low pressure on the glass, fed from a ground unit. The pilot and the ground crew stayed at platform level the whole time.
400 m² of glass were cleaned in a single night. No train was delayed, and no one worked at height during spraying.
Why it matters for Thailand
Bangkok has the same kind of building: BTS and MRT stations, airport terminals, shopping-mall glass roofs and atriums where closing the site for cleaning is not an option. The method used at Saint-Lazare transfers directly: night work, no traffic interruption, nobody at height, and a cleaning rate of 500 to 800 m² per hour on large glass surfaces.
In the press
RATP has since commissioned CleanAlta on other sites, including Marne-la-Vallée Chessy station. Photo on the references page: glazing cleaned by drone on another Paris site.
Questions about this job
How can a drone clean glass above live railway tracks?
The drone is tethered to a ground unit that supplies power and water, so it cannot fly away, and it works at night between the last and first trains. The crew stays on the platforms; nobody climbs on the structure.
What does “intervention time divided by five” mean?
It is RATP’s own comparison between the single night needed by CleanAlta and the time its usual method would have required for the same 400 m² of glazing.
Could the same be done at a BTS or MRT station in Bangkok?
Technically yes: the method is identical. In Thailand it requires NBTC and CAAT registration, third-party insurance and a permit for the urban flight, which CleanAlta handles before any pilot job.
Investors, property groups and corporates
We present the Thai launch plan and the figures in a direct meeting, under NDA. Building owners can also apply for a documented pilot job.