A word to motorists on the A4 motorway in the east of Paris! Starting this Monday, October 12, 2026, Sanef is launching a new phase of works on the future Sycomore diffuser, at the place of Bussy-Saint-Georges (Seine-et-Marne). As a result: several night closures of the A4 are planned until October 23, first in the Paris-to-Reims direction, then in the Reims-to-Paris direction.
These interruptions will allow the teams to carry out the road surfaces necessary to connect the new interchange. Detour routes are being put in place to enable drivers to bypass the construction site.
Over the nights of October 12–16, 2026, the A4 will be closed in the Reims-bound direction, with a mandatory exit at the A4/A104 interchange, from 10:30 p.m. to 5 a.m. The entrance ramps to Reims from the A104 and the Ferrières-en-Brie interchange (exit 12) will also be closed, from 9:30 p.m. to 5 a.m. Motorists must follow the detour in place to reconnect with the A4 at Serris (exit 13). The Ferrières service area will also be inaccessible from 6 p.m. to 5 a.m. during the affected nights.
Next week, the works will switch direction. During the nights of October 19–23, 2026, the A4 will be closed in the Paris-bound direction, from 11:30 p.m. to 5 a.m., with an obligatory exit at Serris (exit 13). The on-ramps toward Paris from Serris (exit 13) and Val d'Europe/Jossigny (exit 12.1) will close earlier, from 10:30 p.m. to 5 a.m. A detour will allow access to the highway at Ferrières-en-Brie (exit 12). The Bussy-Saint-Georges service area will also be closed from 6 p.m. to 5 a.m. Beyond these overnight interruptions, traffic will continue on 3 lanes, with a speed limit of 90 km/h in the construction zone.
These closures accompany the construction of the Sycomore’s new échangeur autoroutier, a motorway interchange located between Ferrières-en-Brie and Val d'Europe/Jossigny. Led by Sanef and EpaMarne, this development is set to improve access to Bussy-Saint-Georges and to the forthcoming zoned development area of La Rucherie, intended to host new economic activities.
The project includes building an structure to cross the A4, new traffic lanes, connections to Avenue Gutenberg and the future business zone, as well as upgrading the basins to meet environmental standards. The exit ramp of Val d'Europe depuis Paris must also be widened to two lanes.
Motorists are urged to plan ahead for their trips over the next two weeks, especially in the evenings and early mornings. The announced dates and times may be revised depending on site conditions. To monitor any changes to closures, Sanef recommends visiting its Sycomore works page, listening to Sanef 107.7, or contacting its customer service at 09 708 08 709.
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Dates and Opening Time
From October 12, 2026 to October 23, 2026
