So you’ve got a dry cough, and breathing is just a little more difficult than usual. Is it coronavirus? You might be able to hop in your car and get a drive-through coronavirus test.

It’s safer—for you and for others—than heading to your local ER. “We’re planning for a potential uptick in the number of severely ill individuals with coronavirus, and we need to reserve those resources for those who need it most,” says Megan Mahoney, the chief of primary care at Stanford Medicine, who provides medical direction to Express Care’s drive-through clinic. Plus, there’s risk in putting the actually infected and the merely potentially infected in the same room, setting up a situation in which people who don’t have the virus could pick it up.

That’s why various institutions around the country have set up mobile testing sites where patients can be tested from the comfort of their own car. Since Seattle, the epicenter of the U.S. outbreak, opened the first drive-through coronavirus clinic last week, other sites have opened in Cape Cod, Palm Beach, Hartford, Rochester, Minnesota (home to the Mayo Clinic), New Rochelle, and Anchorage, with new ones announced every day.

The logistics vary from site to site. The most important thing is to find out what needs to happen before you drive up. Most testing sites require patients to have a pre-screening phone call or video chat with a doctor, who can then assign the patient an appointment time at the drive-through clinic. Other sites, like Denver, allow anyone with a doctor’s note to queue up for a test, and perform pre-screening on-site. (Denver’s system has been so overloaded that the site closed early on Saturday and remained closed on Monday and Tuesday.) Once patients are deemed eligible for testing, they typically show identification through a closed car window, then drive forward to the testing space where a medical professional suits up and swabs inside their nose. From there, samples are sent to local labs for testing, and the wait time for results is variable; Stanford aims to text patients their results within 24 hours, while UW Medicine patients can expect to receive results online in 2-3 days.

The number of tests these clinics can handle varies, though in coming weeks, clinics hope to ramp up their capacity. Stanford opened its testing site a week ago and has been nose-swabbing 100-200 patients a day; it hopes to increase that number to thousands a day. UW Medicine’s clinic just opened Monday afternoon; it tested 15 people in half a day, and there were 30 people on the schedule for Tuesday. It’s equipped to test up to 60 people a day depending on staff availability, with new sites planned for the near future.

After the federal government botched its launch of COVID-19 tests in early February, labs across the country, sensing the urgency, took matters into their own hands, finding ways to circumvent federal guidelines that stood in the way of their work. On the last day of February, the FDA announced that it would allow individual labs to develop their own tests and use them immediately after approval. The lack of early testing likely hastened the spread of the novel coronavirus, as tests allow us to identify who is infected so they can self-isolate, and also gives public health officials a chance to contain local spread by alerting the infected person’s contacts that they, too, may be infectious. In places like Seattle, the “genie is a bit out of the bottle,” pandemic expert Dena Grayson told Vox last week, so testing might be too little, too late. But it can curb the spread in less impacted cities, she says, by catching people and convincing them to self-isolate earlier.

There seem to be few federal mandates on what form these clinics should take. On some level, this makes sense. Local medical providers know their populations best and should have some freedom in designing a system that works for them. But I was surprised to learn that some protocols had no federal standards. For instance, when I asked Stanford’s Mahoney about which parts of their protective gear health care providers change in between seeing patients, she said, “That’s a tricky question to answer, because the CDC guidelines are not so straightforward. We leave it up to the individual provider to decide what they change, but at minimum, they must change their face shield and gloves.” Whether they change their N95 mask beneath the clear face shield or their gown is the discretion of the health care professional. In most cases, it’s unlikely those would be contaminated—they’re taking a nose swab, after all—but the lack of federal directives on drive-up clinics shows how the rules are being created as clinics put together these emergency testing sites.

Mahoney also says that Stanford is in close contact with several other institutions—UW Medicine, Kaiser, and the Mayo Clinic—to share protocols in hopes they can learn from and support one another. Collaboration among scientists is nothing new, of course, but one might expect a federally organized response to this major public health event rather than having that responsibility fall to a few well-resourced organizations.

Though drive-throughs make testing easier and safer, the number of tests each site can process is still limited. Each site’s capacity depends on the availability of professionals to swab patients, as well as the availability of technicians to perform those tests. In many places, there’s a shortage of labor, and of supply. To meet demand in Seattle, UW Medicine solicited help from the greater university community, asking any available qualified individuals for “voluntary reassignment” to COVID-19 testing, and UW researchers faced a pipette shortage for lab work over the weekend. Because test capacity is limited, sites are rationing their resources, focusing on high-risk patients: those with other health issues, like kidney disease, heart disease, or diabetes; those who have a high risk of exposure to the virus, like first responders and medical professionals; and those who are over 65. (Of course, there are exceptions, too, like entire NBA teams being tested within a day, while average citizens grow increasingly frustrated with their inability to be tested at all.)

With capacity ramping up, clinics will likely expand their criteria for who is eligible for testing. “In the near to medium term, we should work to develop the capability to test everybody with suspected symptoms,” says Thomas Hei, associate medical director for ambulatory services at UW Medical Center, and (“It doesn’t get more ambulatory than a trailer in a parking lot,” he told me from his new make-shift office near the drive-through clinic.)That way, we can know more definitively who needs to self-isolate. I asked Hei about testing for people who don’t have a car, but don’t necessarily want to walk into a clinic, either. “We care a lot about health equity and this is what we have now, but we’re actively trying to make plans for other modalities for testing,” he says. For instance, there’s talk of developing a system where people could self-administer a swab test, but the logistics are difficult: How do you design a testing system that’s efficient and keeps everyone safe? Contaminated tests could endanger technicians analyzing the swab, as well as whoever helps deliver samples to the lab, including mail carriers.

If you’re concerned about your symptoms and want to get tested, be sure to check with your local testing clinic about their policies. Most likely, you’ll need to check in with a doctor before showing up. “We have had a few instances of people coming after hearing about it and saying, ‘I want a test,’ and we have had to turn them away,” says Hei. “At least one individual was not very happy about it.” Don’t be that person—medical professionals have enough to worry about right now.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.