Mature drivers are the driver group most at risk to be involved in fatal crashes when accounting for distance travelled. While advanced driver assistance systems (ADAS) promise to enhance older driver safety, trust in these systems is crucial for their effective use. However, the effects of factors such as trust in automation and attentional capacity on situation awareness (SA), a key factor in driver safety, remain underexplored. This study investigates the impact of trait and state facets of trust in automation and attentional capacity on SA. Participants aged 55+ completed two sessions comprising four experimental drives in a simulator equipped with an advanced cruise control system, while wearing a 14-channel EEG headset running an auditory oddball protocol. In session 1, the automated system functioned as intended (initial trust condition). In session 2, participants encountered system failures during the first two drives (low trust condition) and no failures during the last two drives (trust building condition). After each drive, participants were queried about their SA and trust in automation. State attentional capacity was indexed using differences in P300 amplitudes. Preliminary results reveal a drop in trust and SA at the end of the low trust condition, followed by a rebound effect. Lower P300 amplitudes in the low trust condition suggest an effect of trust on state attentional capacity. Results of this project will provide valuable insights into the interplay between trait and context-dependent factors and their impact on older driver safety, informing the design and development of future ADAS.