Based on the expected level of impact, one has to decide among i) Flexible, ii) Semi-rigid or iii) Rigid type barrier. Withing the Flexible category of barriers one can do the following to improve energy absorption level: a) Reduce post spacing, b)use higher grade material for W-Beam iii) Increase section modulus by playing with the geometry.

Thank you Debasish...!! Is there any material online/Book so that I can read about the different steel grade , section modulus of W Beam..?

Master's thesis or any research work should be started with literature survey, so first of all one must know different codal provisions given IRC: 5, IRC:6 and AASHTO codes etc. Then the work done by various researchers in this area. This will give broad idea about the subject.

The design of W-beam roadside barrier is to guide and rebound the impact vehicle back to the traffic lane. The absorption of energy is more to do with the shell of the vehicle body. The stiffness of the barrier should be uniform and should not be penetrated by the vehicle. Energy absorption of the barrier is not the key issue except at the ends when the barrier is impacted on the front ends of the barrier.

There are standard designs you can find the US and EU as well, they have been tested in field for injury index for the passenger and driver and car's trajectory. Any changes to the W beam stiffness and post spacing will alter both the index and the trajectory, and therefore should be tested otherwise it cannot be used. In the study, the test should at least be done in computer simulation for the impact scene but to do this you need a powerful computer and suitable software, such as LS-DYNA. The rules are 1) its stiffness should be uniformly distributed along the whole length, 2) not too flexible otherwise it cannot reidirect the vehicle back to the traffic lane, 3) not too strong otherwise the injury index cannot pass. Good luck.

W-beam crash barrier should be designed more for the safety of the vehicle which is crossing the crash barrier and it should be highly flexible throughout so that the impact energy is slowly dissipated.Hence the beam should have maximum deflection for absorbing the energy without breaking.This should be the criteria for the Design.Hence the beam should be Designed as a highly flexible beam

I agree with Debasish Mondal. First see AASHTO and DIN standards.

A crash barrier has to meet certain performance standards. It must capture the vehicle, and redirect it onto the traffic lane without sending it across other lanes.  It must not fail under the design crash.. It must not be too rigid when impacted by a light vehicle.  It must not cause overturning.  At failure, it must not result in debris that can cause serious injury to other road users not involved in the crash.  It cannot spear through the crash vehicle.  Ride down accelerations must meet strict criteria.

I suggest that, before you proceed further, you obtain copies of the relevant ASSHTO and EN standards, and spend time with testing experts so that you fully understand the requirements.  It is instructive to see videos of crash tests and the performance results.

For any improvement to be accepted, it must do a better job, last longer and, preferably, cost less than the products on the market.

The improvement to W-Beam is Thrie-Beam.  The recent work has been on terminals and posts.