Yesterday, the CDC released more relaxed mask guidelines for outdoor activities, as well as new charts for indoor and outdoor recommendations. The more permissive guidelines were a welcome step forward, but they’re still frustrating. By issuing recommendations that are simultaneously too timid and too complicated, the CDC is repeating a mistake that’s hounded America’s pandemic response. The new guidelines are rigid and binary, and aren’t accompanied by explanations or a link to an accessible version of the underlying science, which would empower people to both understand them better and figure things out for themselves.

The new guidelines come with charts that list specific activities and how a person should engage in them, based on their vaccination status. The charts illustrate people wearing masks or not, with different colors and mask statuses for vaccinated and unvaccinated people, depending on the activity. The chart for outdoor activities suggests that masks are not necessary for walks or runs, for example, if people are by themselves or with their household, regardless of vaccination status. However, unvaccinated people are advised to wear a mask at “small” outdoor gatherings that include other unvaccinated people, but the people are still marked “safest.” Colors change, too: Yellow is used for the unvaccinated dining outdoors with multiple households, marked as “less safe,” though the earlier “small, outdoor gathering” does not clarify household status. Crowds have everyone masked, but the colors are different: red for the unvaccinated, green for the vaccinated, who are wearing masks but marked “safest.”

Confused? You’re not alone. The guidelines got Linsey Marr, a professor at Virginia Tech and a leading expert on viral transmission, to remark that even she can’t remember all of this. “I would have to carry around a sheet of paper—a cheat sheet with all these different stipulations,” she said in an interview after the announcement.

And despite all the detail, social media was flooded with questions from people who couldn’t figure out what they should do in different settings. What happens if they live with someone who is not vaccinated or has medical issues? What counts as a crowd? How small is a “small, outdoor gathering”? Why are unvaccinated people “safest” at a small outdoor gathering but not at an outdoor restaurant? And why is a crowd a threat to the vaccinated? What does the color coding for unvaccinated people indoors mean exactly, since they are advised to wear masks at all times? The CDC should, at the very least, explain the scientific reasoning behind these rules. Not only would this empower people; it would inform the inevitable debate about the guidelines.

Read: Are outdoor mask mandates still necessary?

We wear masks for three reasons: to protect ourselves from people who might be infected, to protect others from our infections, and to set social standards and norms appropriate for a pandemic. The last one is the most important: A pandemic requires a collective response. As we learn more, we move from broader precautions to targeted mitigations. Early in the pandemic, the existing guidelines that suggestedonly the sick should wear masks and the objection that we didn’t know all we needed about the effectiveness of masks violated both the need for social norms, by stigmatizing the sick, and the precautionary principle, by letting remaining uncertainty stop us from protecting ourselves as best we could even with imperfect knowledge. So we changed the rules.

Now, a year later, both the sociology of outdoor masks and the precautionary principle operate in the opposite direction, because the science is in. We need to change the rules again, but also explain why.

Let’s start with the outdoors. Study after study finds extremely low rates of outdoor transmission. So far, I’m unaware of a single confirmed outdoor-only super-spreading event, even though at least thousands of confirmed super-spreading events took place indoors. (The Rose Garden party to celebrate Donald Trump’s nomination of Amy Coney Barrett to the Supreme Court and the multiday Sturgis motorcycle rally in South Dakota both had extensive indoor components.) When outdoor transmission does occur in small numbers, it’s not from fleeting encounters, but from prolonged contact at close distance, especially if it involves talking, yelling, or singing.

An increasing number of scientists believe that outdoor and indoor transmission differs so starkly because the coronavirus transmits through aerosols—essentially little floating particles that we emit, even if we are just breathing, but even more if we are talking, yelling, or singing. Unlike droplets, these aerosol particles do not immediately fall to the ground with the force of gravity within three to six feet, and they concentrate most around the person emitting them, so close contact remains risky. Crucially, they can disperse quickly if they are released in the great outdoors, or, conversely, they can keep accumulating in a poorly ventilated, enclosed environment and travel beyond the short distance in which droplets would fall.

The risk of transmission depends on the person, place, and activity, and the first is the hardest to be sure about. The rate of aerosol emission varies greatly among people, and the viral load in infected people changes throughout the disease’s progression, peaking right around symptomatic disease for most. Plus, we don’t always know who is vaccinated. But we know where we are and what we are doing—whether we are outdoors and whether we are interacting at close length. So even without taking vaccines into consideration, the previous guidelines that recommended masks in “public settings,” including outdoors, were already too rigid and too timid.

Now that nearly 100 million Americans have been fully vaccinated, we have to factor that into our risk assessment. The CDC has been loosening rules for the vaccinated, and there, too, the guidelines have an implicit message. For example, the CDC does not require vaccinated people to quarantine after exposure or travel unless they get sick. The totality of the evidence so far indicates that vaccinated people are not just incredibly safe from severe disease or death, but they are very well protected against symptomatic COVID-19. These no-quarantine-required rules show that the CDC further believes that the risk of unknowing transmission due to an asymptomatic infection can be considered so minuscule as to be negligible. So perhaps although one can imagine that vaccinated people may transmit COVID-19 indoors in very, very rare cases, it’s harder to imagine the chances of such transmission occurring outdoors to be anything but vanishingly low.

Read: Why aren’t we wearing better masks?

To add to the confusion, in earlier guidelines, the CDC already said that vaccinated people could meet indoors without masks even if one of the households had unvaccinated members. It’s confusing to say that vaccinated people can meet indoors without masks with unvaccinated people in one guideline, but that they should wear masks outdoors in a crowd in another guideline, without further explanation of why. If the idea is that, in crowds, we should keep masks for everyone because of sociological reasons, to avoid the awkwardness of selective mask enforcement, the CDC should just say so.

What about rules for vaccinated people indoors, then? One could argue that the science is already fairly strong that the vaccinated are likely fine even indoors, especially if community transmission isn’t very high, and that the CDC guidelines implicitly assume this. That said, one can concede that this part of the empirical record is still evolving. However, that’s not currently relevant for public rules and behavior, because just like we can’t tell only the sick to wear masks, we cannot tell only the vaccinated to chuck their masks indoors—a grocery-store clerk shouldn’t have to police this. For now, indoor spaces have to keep masks as a rule simply for sociological reasons. We should make that explicit too.

The CDC needs clearer, science-based guidelines that inform and empower us. People do not need a complicated patchwork of charts with rigid, binary rules. The science supports a simple guideline that allows for the removal of all mask mandates outdoors, except for unvaccinated people in prolonged close contact, especially that involving talking, yelling, or singing. (As Marr notes: Either masking or social distancing can be sufficient outdoors.) If you are vaccinated but want to increase your comfort because transitions can feel abrupt, or if you are concerned, for example, because of an unvaccinated or vulnerable household member, you can keep your distance and wear a mask, but a mandate for everyone else is not required. Having the CDC spell this out with nuance is better than strict rules that can create stigma and therefore put unwelcome pressure on people with specific circumstances, such as the immunocompromised. Plus, it’s good to adopt the social norm that, outdoors, we should let people be masked or unmasked, especially because shaming and scolding in either direction is unwarranted.

Finally, the CDC guidelines are not just timid and inconsistent. They are late: We’ve known about outdoor transmission being a much lower risk for almost a year now. We should move cautiously, for sure, but excessive caution creates fatigue and mistrust. In the United States, case counts and deaths are trending down thanks to our impressive vaccine supply, and because of the tragic reality that millions have already attained some level of immunity from being infected. Over the past year, we’ve also gained tremendous understanding about transmission risks—where they are high and where they are very low. It’s time that our rules reflect that reality, and spell out their reasoning explicitly, so they can inform and empower us as we trudge through the rest of this miserable pandemic.