The driver app tries to contact the main system every 5 or so seconds depending upon signal strength and connectivity.
Every 5 seconds there’s on average a data transfer of 5kb.
Doing the maths, over a span of 12 hours, if used every day, the driver’s mobile phone may use in the region of 8mb.
So, the driver app uses approximately 8mb of data per day. Over a month that equates to about 240mb/month, which falls way under even the lowest data allowance given by mobile providers.
To summarise, the driver app can use on average:
240Mb of mobile data per month.