Traffic can be improved taking the following points in mind:
1- Use of school busses instead of privet cars.
2- Alternate between cars with Odd and even plate numbers to run on different days, i.e. plats end with Odd number can run on Sun, Tue and Thu, and plates end with even numbers can run on Sat, Mon and Wed.
3- Make a loop highway around Doha, with certain exits and few points.

This is only my opinion