Wireless vehicular communications pose significant challenges for the deployment of next generation roadside services. Some important issues that must be tackled are security, billing, and reliability while guarantying a scalable service delivery. This paper addresses the assignation of secure service session parameters upon the reception of on-demand service requests by an incumbent services district domain and studies and analyses the performance of the underlying mechanisms. Three types of service request protocols are introduced in our work defined as single-hop (SHI-RQ), extended connectivity (EC-RQ), and multi-hop (MHI-RQ) service requests. A detailed analytical model and cost study for the access protocols are presented. Our analysis study covers the estimation of total cost in terms of latency for each access protocol with different mobility characteristics and vehicle densities within the service coverage area and across different serving district domains. The analytical results are consistent with the experimental one and show that the access protocols cost in terms latency remains acceptable for a realistic number of serviced vehicles even at high speeds. Copyright © 2009 John Wiley & Sons, Ltd.