Proposed seat design of additional third-row seats.

Guidelines for the construction and installation of after-market additional seats are provided under Vehicle Standard Bulletin (VSB) 5A Commercial Manufacture and Installation of additional seats and VSB 5B Construction and Installation of additional seats by Individuals. These VSBs (referred to as VSB 5) recognise three categories of additional seats:
 Category 1: Additional seats intended for use by adults;
 Category 2: Additional seats intended for use by children up to 12 years of age;
 Category 3: Additional seats intended for use by children up to 8 years of age.
The NSW Centre for Road Safety has been examining the crash protection afforded by these seats. For children under 4 years old, our previous study found that a child occupant sitting in a child restraint on a Category 2 or Category 3 seat (Additional Seat) was better protected than a child occupant sitting directly on an Additional Seats, but was not as well protected as a child in a child restraint in a standard vehicle seat (Suratno, 2011).
There is also an issue for children aged between 4 and 7 because the space requirements for Additional Seats under VSB 5 make it impossible to meet the general requirement that children must be secured in a suitable approved child restraint or booster seat. Hence, some states in Australia have amended the laws allowing children aged between four and seven years to occupy these seats without using a child restraint or booster seat provided they are wearing a lap/sash seatbelt or a lap-belt in conjunction with a child safety harness. However, even when seated directly on the Additional Seat, the space requirements for VSB 5 may not be sufficient to ensure acceptable safety for children aged between 4 and 12 because they are at risk of being injured by striking the seat in front or the vehicle roof.