You can use Voronoi polygons tool under Vector geometry (or a GRASS version of the tool) in qgis to create a diagram of areas closer to each given point. It will not reflect areas that are faster to reach, though, but it will give you a rough approximation of service areas. There is a solution that calculates voronoi diagram based on travel time on roads instead of based on distance in Maptitude GIS (https://www.caliper.com/learning/media/areas-of-influence-and-network-partitions/), but it's not free. I think it might be possible to use ORS routing or QGIS service area calculation to create a custom Python script that calculates an accurate travel time based isochrones, but it's above my paygrade. If you came to know a better solution, please do let me know.

You can use Voronoi polygons tool under Vector geometry (or a GRASS version of the tool) in qgis to create a diagram of areas closer to each given point. It will not reflect areas that are faster to reach, though, but it will give you a rough approximation of service areas. There is a solution that calculates voronoi diagram based on travel time on roads instead of based on distance in Maptitude GIS (https://www.caliper.com/learning/media/areas-of-influence-and-network-partitions/), but it's not free. I think it might be possible to use ORS routing or QGIS service area calculation to create a custom Python script that calculates an accurate travel time based voronoi isochrones, but it's above my paygrade. If you came to know a better solution, please do let me know.