What we ought to do in Britain (perhaps) is to adopt the Continental method. The A22 from Spain into Portugal has no toll booths and thus no cash option from Dec 8th 2011. You have to organise either a transponder for your vehicle or prepay.
Here is the rigmarole you have to go through although the
Porkancheese would have you believe it is easy.
This may be of use to people traveling to Portugal - Via Spain
Esteemed Customer,
Thank you for your contact, which deserved our full attention.
Please be advised that in order to purchase one of our virtual prepaid solutions for vehicles registered abroad, you must:
1 - Register on the CTT website
www.ctt.pt2 - Access the link:
http://portagens.ctt.ptand select the option "Serviços disponiveis - matriculas estrangeiras" in the menu on top of the webpage.
3 - Enter the username and password chosen when registering on the CTT website (or register on the website if you have not already).
4 - Fill out the form with information of your vehicle (country of registration, license plate number, phone number and class of toll - respectively) and click "Seguinte".
5- Select the first date when you shall pass through the toll (by clicking on the timetable icon) and then select the type of prepaid that you want to purchase. After this selection, click "Seguinte".
6- Finally, complete the purchase by indicating the details of your credit card (you can also check the terms and conditions of the prepaid you selected to purchase).
Remember that for any clarification or more detailed information, please visit our website
http://portagens.ctt.pt or call CTT Line, available weekdays and Saturdays from 8am to 22pm, on 707 26 26 26.
Best regards,
Vanessa Vicente
Customer Service