Can I install the double brakes on the tt handlebars? I have a fixed gear bike. I want install a tt handlebars, but I don't know it can install double brakes?
As long as you can find a way to physically attach the brake levers you want to use you should be able to install a dual brake lever system on your bike. There are so called 'inline brake levers' which you could use for this purpose, they don't require you to buy a brake line splitter which makes them easy to install. They look like this:


Alternatively you could use a 'brake cable splitter', something similar to this:

Another option:

                
            
Yet another:


The 'cable splitter' approach is needed if you want to use 2 sets of bar end levers, since these (to my knowledge) don't come in inline versions.