How to disable traffic alert messages which come as flash sms from carrier?
This looks like a special kind of SMS message, sometimes called "flash SMS", that shows up instantaneously on the phones screen. I don't think that there is an option to block these messages and even if it would be possible I wouldn't encourage you to do so, because you could maybe miss some other important information.

I think the best approach would be to ask your carrier from disabling these messages for your number. I am sure that they are able and happy to do so.