How to specify multiple scopes when triggering the OAuth 2.0 flow

The documentation says that in order to initiate an OAuth 2.0 flow you need to use a URL like this

https://gomotive.com/oauth/authorize?client_id=<YOUR_CLIENT_ID>&redirect_uri=<YOUR_REDIRECT_URI>&response_type=&scope=<YOUR_SCOPES>

However, I'm having trouble when I try to specify more than one scope.

I've tried "&scope=users.read,vehicles.read", "&scope=users.read+vehicles.read" and "&scope=users.read&scope=vehicles.read". In these cases I've received the message "The requested scope is invalid, unknown, or malformed."

What is the proper way to handle multiple scopes?