Bridges on the N’Djamena-Moundou-Sarh road

Design for the widening of three (3) bridges on the N’Djamena-Moundou-Sarh road



Name of Client

Ministère des Infrastructures des Transports et de l’Aviation Civile

Financing sources

African Development Fund


09/2014 - 02/2016

Project Description

The project concerns the widening to two lanes of three one-lane existing bridges realized from 1950 on the road N’Djamena – Guelengdeng – Bongor – Moundou –Doba – Koumra – Sarh of 778 km, with the aim of improving road security condition and, with speed increase, determining transport costs reduction and improving, from an economic point of view, the connection with Cameroon and Central African Republic.


The bridges are :

-  MULKOU, located at Ch. 40+400 of the Guelengdeng-Bongor road, existing bridge : length 72.80, width 3.50 m (3.50+2x0.50)

-  DOBA, located at Ch. 91+100 of the Moundou – Doba raod, existing bridge : length 142.20, width 3.50 m (3.50+2x0.50)

-  MANDA, located at Ch. 87+150 of the Doba-Sarh road, existing bridge : length 342.20, width 3.50 m (3.50+2x0.50)


The project included :

-  MULKOU, widening of the existing bridge from 4.50 m to 11.00 m (7.00+2x2.00);

-  DOBA, construction of a new bridge parallel to the existing one, with mixed structure with 142.20 in length and (9.00 /7.00+2x1.00) in width;

-  MANDA, construction of a new bridge parallel to the existing one, with mixed structure with 342m in length and (9.00 /7.00+1.00) in width.


Connection existing access road – new bridge:

-  DOBA, length of approximately 500 m, width of 10.00 m (7.00+2x1.50), wearing course in double surface layer;

-  MANDA, length of approximately 1.000 m, width of 10.00 m (7.00+2x1.50), wearing course in asphalt concrete (BB).

Services Description


  • Diagnostic of existing structures,
  • Basic technical studies : topographic, hydraulics, geotechnics for access roads and construction materials, geotechnics for foundations (mechanic surveys with laboratory analysis and geophysics), environmental and traffic studies;
  • Elaboration of the Preliminary design (APS) of various construction alternatives;
  • Economic study ;
  • Final design (APD) of the chosen alternative;
  • Conception of works bidding documents.