Im missing the curved Railroads......

[Dildobaggins]

I dunno whats wrong, i have everything except for the curved Railroads, and i've checked.. The Railway research only unlocks normal Railroads.
Please help

[Rockstar04]

If you are using the experimental version 0.13, then the rail building mechanic has been changed, and you can create curved rails with straight rails when placing track.

Check out this page for an animated example of the new rail building: http://guide.factorio.com/new-features-013.html (scroll down to "Better Rail Building")