The iOS 14.5 beta, available to developers and public beta testers, adds a new Apple Maps feature that lets you report accidents, hazards, and speed checks along your route when getting directions.
When you input an address, select a route, and then choose "Go," Siri lets you know that you can report accidents or hazards that you see along the way.
If you swipe up on the Apple Maps interface where maps details are available, you can tap on a "Report" button that lets you flag an accident, a hazard, or a speed check, similar to other mapping apps like Waze. Tapping automatically flags your location with no confirmation window, so it shouldn't be used except in a valid situation.
You can also say "Hey Siri, there's an accident" and Siri will send in a report to Apple Maps, and presumably, if enough people file reports, an accident site will show up in the maps app through the crowdsourcing. This is available in the United States in a test capacity at the current time, and it's not yet clear if it's also showing up in other countries.
This also works in CarPlay, as noted on the MacRumors forums by MozMan68, with the reporting interface available on the CarPlay screen.
Note that Siri will inform you about the new accident reporting functionality the first time that you seek directions after upgrading to iOS 14.5, but the feature is not mentioned after that. There is no similar accident reporting functionality available in iOS 14.4, and it also does not appear to be showing up for all iOS 14.5 users at this time based on reports from Reddit, so there is likely a server side element.
