In the greater Paris area – the Île-de-France region – the long-awaited new Tzen 4 Bus Rapid Transit line commenced operation on 10 February 2026: it substantially improves mobility in the Essonne department south of Paris. The line connects the towns of Viry-Châtillon and Corbeil-Essonnes over a distance of around 14 kilometres, passing through Grigny, Ris-Orangis and Évry-Courcouronnes. It thus serves densely populated residential areas, important employment centres and several rail interchanges.
The Tzen 4 is part of the so-called ‘Bus à Haut Niveau de Service’ (BHNS), a bus system with particularly high quality and performance, also known internationally as Bus Rapid Transit (BRT). Most of the route runs on dedicated bus lanes, which largely avoids traffic jams. In addition, the buses are given priority at traffic lights at many intersections. This ensures significantly higher punctuality and shorter journey times compared to the previous bus line, which the Tzen 4 is gradually replacing.
Thirty modern bus stops have been built along the route. These are barrier-free, have dynamic passenger information displays and offer greater comfort and safety for passengers. The buses used are 24-metre-long electric double-articulated buses with a capacity of up to 140 passengers. This means they offer around 40 per cent more space than the previous vehicles. The order for the vehicles was originally placed with Belgian manufacturer Van Hool, but the company had to file for bankruptcy. At that point, only one vehicle had been completed, with others at various stages of construction at the manufacturer’s plant. The Swiss company Hess AG finally took over completion of the vehicles at Van Hool’s Belgian factory and delivered all of them in 2025. One bus had already been on display at Busworld in Brussels in 2023.
The buses are fully electric and are charged in around five minutes at selected stops using a fast-charging system. This is the SRS (static charging system) developed by Alstom.
In addition to air conditioning and spacious interiors, USB charging ports and modern information systems are also available.
The service operates daily from early morning until around 1 a.m. During peak hours, buses run every five minutes, ensuring high transport capacity. In the long term, around 50,000 passengers per day are expected. The new line also improves connections to other modes of transport such as the RER D, the T12 tram line and the Tzen 1, thereby strengthening the entire transport network in the south of the Paris metropolitan area. Currently, the existing bus line 4206 continues to operate every 15 minutes from Monday to Friday , in addition to Tzen 4 to ensure a smooth transition to the new system.
With investment costs of around €123 million, borne by the Île-de-France region, the Essonne department, the French state and the European Union, Tzen 4 is seen not only as a pure transport project, but also as part of a comprehensive urban development strategy.
