Here are a few high level use cases for Web Payments from Connected Vehicles. It is not meant to be exhaustive but to facilitate early conversations.

see also TPAC 2015 Web Payments and Automotive liaison minutes

https://www.w3.org/2015/10/26-wpay-minutes.html#item01

and Kevin Gavigan (JLR) slides

https://www.w3.org/2015/10/payments-auto201510.pptx

Distractability

Web Payments includes user confirmation to complete a transaction. For fuel/charging, parking and other charges when the vehicle is stationary that is reasonable. When the vehicle is traveling at 70 mph on a highway for example and an electronic toll collection system seeks payment however there should be verbal or no confirmation as interacting with the driver is a distraction. Profile settings could permit limited, automated transactions of certain types while the vehicle is moving.

Usage

Congestion and usage charge models are being implemented in various countries or cities and likely to increase with electric vehicle adoption since that will result in lower fuel tax revenue.

Connectivity

Connected Vehicles will frequently be offline due to cellular coverage. This complicates completing payment transactions that might arise. A gas station in the dessert for example is likely to have a land line for credit card processing and could provide wifi to the vehicle. A promise of payment can be made when connectivity is an issue and completed once the vehicle is online again. The merchant can store license plate information and other data communicated by the vehicle (via NFC, BT or wifi) to limit fraud.

Carshare / Rideshare 

We are seeing an increase in various car share models where there are multiple users instead of a single owner. There is also various carpooling/rideshare applications emerging to handle appropriate prorated travel costs. The head unit (vehicle computer) could temporarily store a user's Web Payment profile, erasing it after the driver is finished using the shared vehicle. Alternately the head unit can pair with a smartphone in order to forward or proxy payment requests.

Fueling / Charging

There are various prototype and production robotic fueling/charging stations which would be complimented by a vehicle being able to complete the financial transaction without the driver needing to leave their car to swipe a credit card.

Loyalty programs / Discounts

Many fuel service companies have loyalty programs to reward customers repeated patronage. There are also corporate and other discount programs in which a driver or vehicle would be eligible for a reduced rate for fuel, parking, toll or other charges. An identifier that can be verified by the merchant should be transmittable by the vehicle when appropriate.