A method for issuing pseudonymous authorisation tickets (AT n ) to nodes (N i ) of a cooperative intelligent transport system, ITS , which nodes (N i ) exchange messages (M k ), each of which is signed with one of said authorisation tickets (AT n ), the method comprising: a) receiving a ticket request (TR) from a node (N i ) in an authorisation server (AA) of the ITS , which ticket request (TR) contains enrolment credentials (EC) of the requesting node (N i ), wherein the enrolment credentials (EC) are encrypted with a public key (K pu ) of an enrolment server (EA) of the ITS , and sending a validation request (VR) containing the requesting node's enrolment credentials (EC) to the enrolment server (EA); b) decrypting the enrolment credentials (EC) contained in the validation request (VR) with a respective private key (K pr ) in the enrolment server (EA), conducting a validity check which is only passed when both the requesting node (N i ) identified by the decrypted enrolment credentials (EC) and, for the requesting node (N i ), an account (AC m ) at an account server (AS) are enrolled with the enrolment server (EA), and, in case the validity check is passed, incrementing a counter value (CV) of a counter (CT m ) assigned to said account (AC m ) and sending a validation message (VM) to the authorisation server (AA); c) issuing , when the validation message (VM) is received in the authorisation server (AA), a pseudonymous authorisation ticket (AT n ) to the requesting node (N i ); d) repeating steps a) to c) until a predetermined charging period (CP) expires, and, upon expiry, sending , from the enrolment server (EA) to the authorisation server (AA), a message (ME) containing said counter value (CV) and an identifier (I AC ) for said account (AC m ) , calculating, from the counter value (CV) received in the authorisation server (AS), a charging request (CR) for the account (AC m ) identified by the received identifier (I AC ), and sending the charging request (CR) to the account server (AS) for charging said account (AC m ). a) receiving a ticket request (TR) from a node (N i ) in an authorisation server (AA) of the ITS , which ticket request (TR) contains enrolment credentials (EC) of the requesting node (N i ), wherein the enrolment credentials (EC) are encrypted with a public key (K pu ) of an enrolment server (EA) of the ITS , and sending a validation request (VR) containing the requesting node's enrolment credentials (EC) to the enrolment server (EA); b) decrypting the enrolment credentials (EC) contained in the validation request (VR) with a respective private key (K pr ) in the enrolment server (EA), conducting a validity check which is only passed when both the requesting node (N i ) identified by the decrypted enrolment credentials (EC) and, for the requesting node (N i ), an account (AC m ) at an account server (AS) are enrolled with the enrolment server (EA), and, in case the validity check is passed, incrementing a counter value (CV) of a counter (CT m ) assigned to said account (AC m ) and sending a validation message (VM) to the authorisation server (AA); c) issuing , when the validation message (VM) is received in the authorisation server (AA), a pseudonymous authorisation ticket (AT n ) to the requesting node (N i ); d) repeating steps a) to c) until a predetermined charging period (CP) expires, and, upon expiry, <EOS>