Road crashes and road accidents

"Road accident" and "road crash sound odd to me. I think "traffic accident" is more common in the US, at least. It is in this ngram (I changed the start form 1800 to 1900.) If you toggle between British and American English, you see something interesting--until around 2000, "road accident" was more common in BE, but then it suddenly nosedives and "traffic accident" is on top.

"Crash" or "car crash" is commonly used, but it's more informal. In fact, "car crash" is the most common phrase overall, more so in AE than BE.

"RTCs" is the favoured acronym in Ireland these days - "road traffic collisions". "Accident" is no longer viewed with favour in official circles because it's seen as suggesting that crashes are inevitable or aren't anyone's fault, so to speak. "Collision" rather than "crash" is the term used instead, though.

I'm English and would probably expect to hear something like 'road traffic accident' in an official context. I haven't checked the frequency of this usage though.

My sense of these terms in the US is a little different from what nutrax said. I hear adults normally talking about a car accident, or just an accident. I had one a couple of years ago, and that is the only term I remember hearing used.

Traffic accident sounds official to me, like something in a government report.

Car crash sounds to me like something children say, especially when playing with toy cars and making them crash on purpose.

"Car crash" turned up a lot in news stories--especially headlines.

Car crash backs up Interstate 10 traffic‎

Knoxville attempted robbery, car crash injures two‎

An 18-year-old woman was killed and two other people were hurt overnight in a single car crash in San Jose.

A Norwich firefighter has died in a four-car crash and another man was seriously injured.

Traffic accident sounds official to me, like something in a government report.

That's why I think it's the most analogous to the links in the OP--official stuff.

Wikipedia gives this:
A traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision (RTC) or car crash...

Many different terms are commonly used to describe vehicle collisions. The World Health Organization use the term road traffic injury,[while the U.S. Census Bureau uses the term motor vehicle accidents (MVA) and Transport Canada uses the term "motor vehicle traffic collision" (MVTC). Other terms that are commonly used include auto accident, car accident, car crash, car smash, car wreck, motor vehicle collision (MVC), personal injury collision (PIC), road accident, road traffic accident (RTA), road traffic collision (RTC), road traffic incident (RTI), road traffic accident and later road traffic collision, as well as more unofficial terms including smash-up and fender bender.

Some organizations have begun to avoid the term "accident". Although auto collisions are rare in terms of the number of vehicles on the road and the distance they travel, addressing the contributing factors can reduce their likelihood. For example, proper signage can decrease driver error and thereby reduce crash frequency by a third or more. That is why these organizations prefer the term "collision" rather than "accident".

I think headlines are a special case, though. They're written with specific constraints and can use words that aren't typical in normal English (like "nab" "slay" "top cop" and so on.) They can differ from regular sentences by not including verbs and/or articles too.

Both are unsatisfactory.

accident implies that there is no blame
crash implies a collision.

Incident is better.

crash implies a collision.

But that is exactly what is being talked about, not just an "incident" that disrupts traffic.

An incident is an event - it does not imply that there is no blame.

A collision would imply more than one car.