Hardly surprising, there are very few differences over and above driving in Spain and I would refer you to the section on Spain on this website rather than repeat all the previous points made and in this section I will only point out the major ones.
We took Brittany Ferries to Santander and combined the trip with a tour of Galicia in Spain.
http://www.brittany-ferries.co.uk/
Touring Requirements are as for Spain with a reminder that if you take bikes, make sure you have the red and white warning sign.
The roads are generally in good condition, though you may come across cobbled paved roads which makes the motor home rattle as never before, so slow down but this does not stop the locals, who still race down these roads at a fair old pace.
This brings me on to driving habits as a whole and as a generalisation you need to keep your wits about you a little more than in Spain but it is nothing you will not experience in the UK and bearing in mind, as in Spain there is considerably less traffic than there is in the UK, so driving is a much more pleasurable.
This confused the life out of me before I went but like all fears of the unknown, once conquered you wonder what all the fuss was about.
The Portuguese have two systems of motorways, the first is the traditional toll booth system as used in France, so on these you can pay in cash or using a credit card, so fairly straightforward here.
The second sort is the electronic system, where there are no toll booths but clear signs that you are entering and in any case you will see the gantries above the motorway. It is quite an ingenious system. The Portuguese needing to raise money after the banking crash, installed them on their ‘non motorway’ arterial roads, the system is basically cheap to install and avoiding traditional toll booths, cheap to administer.
The Portuguese and the Spanish were not too keen on the imposition of tolls and try to avoid them and the end result is that the motorways are very lightly trafficked.
How to pay for them? This is where the confusing part arises if you are a driver of a foreign vehicle. Without going into all the detail I would refer you to the Portuguese site:
http://www.portugaltolls.com/en/web/portal-de-portagens/home
Basically there are two options: the Easytoll system or the prepaid card. The 3 day card was of no use and I discounted the prepaid cards, as I simply did not know to what extent I would use them, so this left the Easytoll, which would be the recommended method.
The only downside of this system is that there are only 4 (at the moment) booths at the border with Spain, where you can register, so if you join the motorway further down or you do not enter Portugal on one of the easy toll motorways then you have a problem, so you do have to plan accordingly.
Algarve em Vila Real de Sto. António (A22)
Vilar Formoso (A25);
Chaves (A24)
Viana do Castelo (A28)
Entering Northern Portugal from Spain we used the booth on the A28 at Viana do Castelo and it could not have been easier, as signs lead you to an automatic booth area, where you enter your credit card and it then links it to your registration. Keep your receipt as you may have to show this as proof of payment. The machine even wishes you a good journey, so off you go and your credit card is automatically debited as you enter and leave the motorway.
It is a myth that the cameras can not read foreign number plates. What happens if you do not pay, if you are a foreign national, I do not know. There are, however, penalty rates for non payment, ten times the toll, also you could be liable for a spot check
You will also see reference to speed controlled by radar, which confused the life out of me, as I could not see any traditional cameras but it appears that the traffic lights are geared to your speed so if you are going over the speed limit, they turn to red, ingenious!
Somewhere I had read that campsites were generally of a lower standard than say in Spain but we were pleasantly surprised and though in some cases the sites were older, they were always spotlessly clean and reasonably priced. As always be prepared to pay cash at some sites.
Credit cards are widely accepted.
Diesel in reality a similar price to Spain, without getting out the calculator and is referred to as diesel or gasoleo,
Security No issues other than the usual precautions that you would take anywhere in Europe.