A user_id is a unique identifier, assigned to each Car and Driving customer.
If you are a prospective customer of Car and Driving and want to try out our service, we can set you up an account - simply contact email@example.com. To set up your account, we need to know the IP Address of the machine (usually the server, or a development machine) calling the webservice.
To find out the IP address of your machine, the simplest method is to visit www.myipaddress.com in a web browser on the machine itself.
Please send us that IP address when contacting us. If you are a development house working on behalf of a client, we would prefer to give you and your end client separate accounts if possible - this will help reporting. Please send us details of yourself and your client if possible.
You can of course give us several IP addresses, or a range of them, if necessary.