Cell towers in Bailly (Yvelines)

2 road gantries and 3 pylons, 1 bridge or viaduct and 1 mast carry the commune's antennas.

Masts stand at 18 Route de Saint-Cyr, A13/Triangle de Rocquencourt and 18 Route de Saint Cyr.

5G is on 71% of masts here, against 88% across Yvelines towns with five or more masts.

ANFR lists a 30 m pylon at A13/Triangle de Rocquencourt as the tallest structure. The median is 10 m, slightly below the Yvelines median of 25 m.

Systems from 1998 are still on the register. Free Mobile opened 5G here in December 2020; SFR followed in July 2024, Bouygues Telecom followed in July 2024. 2017 was the busiest year, with 12 new systems, most of them 4G.

Approved additions not yet in service are pending on 3 existing masts, for example Free Mobile (4G 2100 MHz), Free Mobile (4G 2100 MHz) at Pmv Sirius A12 Pk 1.4 Sens Province Paris and Free Mobile (4G 2100 MHz) at Intersection Autoroute A13 Sens Province Paris Pr 13.2 et D. 1 Bouygues Telecom 5G transmitter is listed as technically operational — installed, but not yet declared commercially in service.

Among the 62 Yvelines towns with at least five masts, Bailly ranks 39th by mast count. With 7 masts for 3,731 residents, or 19 per 10,000, it has more masts per inhabitant than the median for those towns (7).

1 km to the west, neighbouring Noisy-le-Roi has 6 masts declared.

Only one mast carries all four networks.

Most declared azimuths point outward, along a corridor or valley rather than at the centre.

Figures above cover installations declared to ANFR as in service or technically operational, as of October 2026; approved projects are not counted.