Lane-changing is performed either to follow the route to a planned destination (i.e., mandatory lane-changing) or to achieve better driving conditions (i.e., discretionary lane-changing). A connected environment is expected to assist during lane-changing manoeuvres, but it is not known well how driving aids in a connected environment assist lane-changing execution. As such, this study investigates the impact of a connected environment on lane-changing execution time during mandatory and discretionary lane-changing manoeuvres. To this end, this study designed an advanced driving simulator experiment where 78 drivers performed these manoeuvres on a simulated motorway in three randomised driving conditions. The conditions were baseline (without driving aids), a fully functioning connected environment with a perfect supply of driving aids, and an impaired connected environment with delayed driving aids. The lane-changing execution time has been modelled by a random parameters hazard-based duration modelling approach, which accounts for the panel nature of data and captures the unobserved heterogeneity. Results suggest that, compared to the baseline condition (i.e., a non-connected environment), most of the drivers in the connected environment take more time to complete their lane-changing manoeuvres, indicating drivers’ safer lane-changing execution behaviour in the connected environment. The communication delay driving condition has been found to have more deteriorating effects on mandatory lane-changing manoeuvres than discretionary lane-changing manoeuvres. This study concludes that (i) the connected environment increases safety margin during both lane-changing manoeuvres, and (ii) a higher magnitude of safety margin is observed during mandatory lane-changing manoeuvres whereby drivers have a higher need for assistance.