The demands on bus interior products have increased with increasing sustainability, circularity and a reduction of harmful substances, today’s materials must be improved with regards of additives, such as flame retardants. A comprehensive study was made to evaluate the possibility to use phosphorous flame retardants (FRs) instead of the commonly used halogenated FRs compounded with ABS. The study showed that the fire performance could be improved with phosphorous FRs regarding heat release and smoke production. However, it was noted that the smoke production still was high, and that the smoke density was highest possible, i.e., no visibility through the smoke layer. Further testing of today’s bus interior materials showed that the high smoke density was achieved already after a few minutes of test time. Thus, it can be concluded that, in case of a fire, the visibility in the bus will be reduced and limit the ability of the passengers to safely evacuate. In addition, several toxic gases were detected in the smoke, both irritants and suffocating gases. The bus fire regulation R118 for interior materials basically deals with burning rate and melting through a fine mesh. Critical fire parameters such as smoke production and smoke toxicity is not dealt with. The R118 regulation need to be improved with these critical parameters in order to have fire safe materials inside the bus.