A few climate milestones were hit within the last week, and not all were worthy of celebration. On Wednesday, the United Nations announced that the Paris Climate Agreement would formally go into effect early next month. The treaty aims to curb rising global temperatures within 2 degrees Celsius and requires countries to publicize their emission targets and progress.

The ratification couldn’t come sooner. Last week, atmospheric carbon dioxide levels reportedly passed the 400 parts per million (ppm) threshold for the foreseeable future. The 400 ppm benchmark isn’t necessarily a heralding of the apocalypse, but it’s surely a sign that we need to change something to lower carbon emissions and rein in climate change.

And like we’ve said before, transportation is an easy place to start. Earlier this year, transportation-related emissions became the leading source of ghg emissions, outpacing power plants for that first time since 1979. Reversing this trend would require people to drive less. That’s easy to do if you live somewhere like New York City and you don’t own a car. In most other locales, you’re going to need better transit and safer streets so that getting anywhere on foot, on a bike or via transit is more than just a feasible alternative, but a convenient one, too.

But if environmental concerns aren’t enough to convince our leaders to invest in diversifying their transportation networks, then maybe yet another ghastly forecast for 2016 traffic deaths will. Yesterday, the National Highway Traffic Safety Administration (NHTSA) announced that for the first half of 2016, traffic deaths rose 10.4 percent compared to 2015. The agency also announced a partnership with USDOT to end fatalities on the nation’s roadways, sidewalks and bike paths within 30 years.

Local and state leaders in the region should follow in these footsteps and commit to funding high-quality transit and safer streets. In doing so, they could end up following through on some weighty environmental pledges while also saving lives.