Safety features include fixed rails and 3 levels for the mattress. (simplybabyfurniture.com)
But despite all the political attention, there is considerable skepticism among economists about the scope for fixed rail to solve congestion. (canadianbusiness.com)
Components like head restraints and car - related gear such as child restraints can be tested on a sled that runs on fixed rails to simulate a crash. (iihs.org)