There are some highways in Portugal on which the tolls are electronic only. It means that there are no cabins and the passing of vehicles is detected by devices placed at the beginning of those highways.
The highways are identified at the beginning with: "Electronic toll only".

The highways concerned:

Norte Litoral (Littoral North-highway)
- A27/IP9: Viana do Castelo - Ponte de Lima
- A28/IC1: Viana do Castelo - Porto

AE Transmontana
- A4: Variante Sul de Bragança

Interior Norte
- A24/IP3: Vila Verde da Raia (border) - Viseu

Grande Porto
- A4: Matosinhos - Águas Santas
- A41/IC24: Perafita/Freixieiro - Sêroa (west)
- A42/IC25: Sêroa (west) - Lousada 

Centro (Costa de Prata)
- A17/IC1: Estádio de Aveiro - Mira – Autoestrada do Litoral Centro (entre Mira e Aveiro)
- A25/IP5: Albergaria-a-velha (A1/IP1) - Vilar Formoso (fronteira)
- A29/IC1: Miramar - Angeja

Centro (Beira Interior)
- A23/IP6: Torres Novas - Guarda

Lisboa Region (Pinhal Interior)
- A13/IC3: Atalaia - Tomar

Lisboa Região (west littoral)
- A8/IC36: Variante Sul de Leiria
- A19/IC2: Variante da Batalha

Algarve (Via do Infante)
- A22: Lagos - Castro Marim


Payment through electronic devices

In order for the vehicles to use the above mentioned highways, they should have an electronic device, which must be bought or hired beforehand at a Service Area (Área de Serviço) alongside the highways or at a post office (CTT/Correios). There are three types of electronic devices:  

Electronic license plate device (Dispositivo electrónico de matrícula - DEM): the device is linked to the vehicle's license plate and cannot be transmitted to other cars.
Obtaining: at the highway service areas or other locations like the post offices and the Via Verde Portugal-shops.
Costs: €27,50 to purchase + preloading a minimum €10 for light vehicles and €20 for heavy vehicles.
Validity: valid for 90 days as from the date of the last preload. After this period the remaining balance will be lost and the device will be deactivated. To reactivate the device it will be necessary to re-charge it with a minimum of €10.

Temporary device (Dispositivo temporário - DT): the best solution for a short stay, and as a result for vehicles with a foreign license plate; the license plate is not linked to the device, therefore, anonymity is guaranteed.
Obtaining: it is necessary to establish a lease contract with the responsible entities, at the highway service areas or other locations like the post offices and the Via Verde Portugal-shops.
Costs: deposit of €27,50 (that will be given back to the driver when the device is returned in good condition within a period of 30 days) + preloading a minimum of €10 for light vehicles and €20 for heavy vehicles. The lease has a cost of 6 euros on the first week, and at the following weeks the cost is about 1,50 euros per week.
Validity: valid for 90 days as from the date of the last preload. After this period the remaining balance will be lost and the device will be deactivated. To reactivate the device it will be necessary to re-charge it with a minimum of €10.

Devices from a toll entity (Dispositivo de uma entidade de cobrança de Portagens - DECP) like Via Verde are also accepted on these highways. Although the license plate is not linked to the device, it is necessary to establish a contract with a toll entity. This can be used by vehicles with a foreign license plate that stay in Portugal for a longer period of time.
Obtaining: Via Verde-shops (www.viaverde.pt) 
Costs: €27,50 + direct debit from bank account every time the device is used.
Validity: Until the cancelation of the contract


Payment without electronic devices:

Three day pre-paid ticket (only available for vehicles with a foreign license plate)
This ticket is valid for three days and may only be used for light vehicles, for several unlimited journeys on the above motorways (only where the tolls are exclusively electronic).
Purchase: Post offices, Payshop chain, Porto Airport and the internet on: http://portagens.ctt.pt
Cost: €20 (plus administrative costs, when purchased over the internet)
It is allowed the purchase of a maximum of 6 pre-paid tickets per year and per each vehicle license plate.

Prepaid credit (only available for vehicles with a foreign license plate)
If the period you are staying in Portugal does not justify the option of the Temporary device, one can opt for charging based on the registration of an image of the license plate in everyone of the electronic toll booths.
Before passing the highways on which the charging is exclusively electronic and through the CTT website, drivers (after being registered on this site and being provided with login and password) can choose one of the following modalities:
- Make a prepayment valid for five days or up to the balance, to the value of €10 (plus administrative costs and joining fee) rechargeable at post offices, Payshop chain and Multibanco. The unused balance can be refunded, to a credit card, in accordance to the details given on registration.
- Make a prepayment for predefined journeys on specific days.
The payment is made through a valid credit card. The amount charged depends on the option chosen.
You can register here (only available in Portuguese): http://portagens.ctt.pt

Payment after having circulated at the roads concerned (only available for vehicles with a Portuguese license plate)
If a vehicle does not have an electronic device when circulating at the highways concerned, a photo of the license plate will be made and saved until the payment is made.
Term for payment: the payment can be made at the second day after having circulated at the roads mentioned above and for a period of five weekdays, at the post office or at one of the shops signalized as “Payshop”.
Costs: normal toll costs + administrative costs (an amount €0,25 for every time the roads were used with a maximum of €2 for each payment made)
Note: when a payment term has passed, the driver is in violation of the rules, and fines will be added to the administrative costs.


Car hire
When hiring a car, please ask the hire company how payment is to be made regarding electronic tolls, as the car hiring company may charge their customers for their use of tolls, as foreseen by Law.


More information:
CTT -  Tel: (+351) 707 26 26 26  or http://portagens.ctt.pt
Estradas de Portugal: http://www.estradas.pt/portagensestrangeiros