Gas station on the outskirts of Beijing.

Four things stand out: Taxi has gas nozzle and redundant petrol cap; tank is noticeably slow to fill; nozzle requires a ‘perfect’ seal compared to petrol; ‘gas station’ is a for once accurate. And it’s bitterly, bitterly cold.

Optimum ways to transfer substances, data?
What feedback to user that the process is proceeding as planned?
What are acceptable error rates for what is transferred?
Risk of errors and consequence when they occur?