Achieving reasonable speech intelligibility in a highly reverberant space is one of the more difficult problems encountered by a sound system designer. With the addition of high ambient noise and a demand for life-safety voice messages, vehicle road tunnels present a clear challenge. Improving speech intelligibility requires optimum type and placement of loudspeakers and acoustic modelling software is a required tool. Where knowledge of the acoustic properties of the materials used in the tunnel is known or can be determined, acoustic modelling provides an assurance of what will be heard. A road tunnel in Auckland New Zealand, AMETI Panmure Covered Box (PCB), is used as a test case where acoustic modelling has provided confidence in achieving high speech intelligibility and this has been confirmed through commissioning measurements.