To be clear from the outset, these instructions are for pumping in a car when you are either a passenger or the vehicle is parked in a secure location. Under no circumstances should you operate a motor vehicle while pumping.
I have found that my car is a great alternative pumping location if I am at a meeting away from the office or at a site that does not offer a proper Mothers’ Room. I have also pumped in taxis on the way to and from the airport and on road trips (when someone else was driving). I have never had an issue pumping in a taxi. Between the noise of the engine and the road, it is nearly impossible to hear the pump and a nursing cover provides extra privacy.
As with all remote pumping activities, process and procedure are key.
The first step is proper set up. Identify an uncluttered flat surface for the pump, preferably in the back seat. Generally, the pumping unit must be kept horizontal and right side up. Tilting the pump on its side or using it upside down can damage the unit. From a safety perspective, in the event of an accident, you could be injured in the front seat if the airbag were to deploy while you are pumping. In a parked car, I prefer the back seat because the windows are usually more darkly tinted and afford more privacy. Remember to lock the doors.
Set up the pump and either plug in the battery pack or use an inverter that plugs into the cigarette lighter (see Pump and parts). Generally, I use the battery pack when pumping in a parked vehicle to avoid the adverse environmental impact of idling the engine.
At this point, I retrieve all of the remaining items I will need to pump and clean up from my pump bag and set them up around me. Then, I get to pumping. If you are concerned about privacy, use a nursing cover. One awkward aspect, if pumping in a moving vehicle, is the seatbelt. If I need to pump mid-drive, I put the hands-free pumping bra over the seatbelt (rather than unlatch the seatbelt, set up, and then re-latch), because I feel safer doing so. If I set up before the drive, then I put the pump bra on first, before securing my seatbelt. It works fine either way.
When you are done, depending on whether the vehicle is moving, putting the milk away can be tricky. Most often, I detach one bottle at a time and hold it between my thighs. The goal is to have the milk uncovered for as short a time as possible. I either cap the bottles and put them in the cooler bag, or pour the milk directly into a storage bag and then put it in the cooler bag. I wipe down the parts and put them in a mesh bag (separate from any clean parts I may be carrying) to wash at my next opportunity.
All of my experiences with pumping in a car have been in the United States. You may need to or want to take a different approach if you are in an area with different cultural norms. You can find guidance and advice from moms who have pumped in these situations on the remote and low-resource environments page.