I am disabled in my right arm (Brachial Plexus) I would like to improve my comfort on my bike.I would also to know about the braking system fitted on one side.
If you using a flat handlebar, something like this would handle your braking needs: Problem Solvers Double Barrel - it's a single brake lever that can actuate two brakes simultaneously.
In the three years since this post the road bike market has increasingly adopted hydraulic disc brakes. Shimano has a good page on their website that addresses a single-hand, dual-lever solution using a mountain bike lever placed under the standard lever.
This blog shows two options for cable road bikes. Both options allow use of both brakes.