On desktop, in the previous versions of Google Maps, you could see transit lines and traffic. I can't find these options in the new version of Google Maps. Where are they?
The interface for showing traffic in the new Google Maps is very poor. The option to show the traffic layer is in fact under the search box, as @sathya says, but not always.
If you have searched for an address, the option is missing:
Delete the address, and the option will appear:
The option is also available when you get directions. In fact, it is turned on when you ask for directions and have the car selected as your mode of transport. In this case, you'll have the option to hide traffic.