Transport Map Layer not available

Hi,

I have used OSM for several years and often use the Transport Layer to show a nice clear map of rail routes. However, today, when I click on the Layer tab on the right hand side, all I can see is Standard and Humanitarian layers.
I presume that this is not a bug and that I’m doing something wrong. Can anybody help me?

I am, and have used for some years, Firefox on Ubuntu.

Thanks,

Chris