Roundabouts have been installed at 87 locations in 31 prefectures since the revised Road Traffic Law took effect in September 2014. Do you think roundabouts reduce the number of traffic accidents?

I honestly didn't notice, but I do think that roundabouts in general are a good idea and PROBABLY do reduce accidents, but I haven't really researched the data to form a definite opinion.

It had been my understanding that roundabouts don't limit the number of accidents, but the severity of those accidents ie. more scraping less smashing...

They do if drivers know how to navigate them. Are they included in the driving test?

The figures are pretty conclusive: https://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm

Single lane roundabouts are more efficient, much easier and safer. The only difficulty is where there are two or more lanes.

They also save on energy and there are no mechanical parts to go wrong.

Please, please, please let's have more roundabouts!

Roundabouts and speedhumps whould definatly slow down those idiots who fly down smaller streets oblivious to pedestrians sharing at best a 3m wide road. But them it might just cause confusion for the general public.

Roundabouts are so much better than traffic lights every hundred meters! Keep the traffic moving.

They are not do much a safety feature as an efficiency measure - as No Business states above, they keep the traffic moving.

MariaToday  08:51 am JST

They do if drivers know how to navigate them. Are they included in the driving test?

When I went to get my license renewed, they did cover how to navigate a roundabout. They also said that most of the roundabouts so far have been placed in eastern Japan. Only one or two in western Japan.

We had one here in the west of Japan many years ago, but drivers ignored the convention and pushed their way in, jamming everything solid. Eventually the authorities gave up and installed lights. Is it a cultural thing?

The outline of the circle is still there, with four flowerbeds. The crossroads still has the name 'Rotary' in it.

Roundabouts with multiple lanes and lots of exits are a nightmare and result in indecision and sudden lane changes. Keep it simple and I think it is safer.

no, instead of wasting money how about putting speed and red light cameras and actively catching the idiots that speed thru.

I like anything that's in the shape of a pizza.

From considerable experience with them here in the UK roundabouts are in many cases better than lights and yes they keep the traffic moving so reduce the over all levels of pollution and especially the buildup with stationary traffic at lights. That being said, like all things they only function if used properly. In a country like Japan where they are not an everyday occurrence than where they are installed there needs to be rigorous and conspicuous enforcement of the rules as well as education.

Rigorous and conspicuous not a strong point in Japan

Roundabouts with multiple lanes and lots of exits are a nightmare and result in indecision and sudden lane changes. Keep it simple and I think it is safer.

I love them. The bigger the better. I long to try the roundabout at the Arc de Triomphe in Paris.

In a country like Japan where they are not an everyday occurrence than where they are installed there needs to be rigorous and conspicuous enforcement of the rules as well as education.

They once didnlt exist in any country but have been introduced successfully around the world.

my favourite is the Magic Roundabout:

https://www.google.co.uk/url?sa=i&source=images&cd=&ved=2ahUKEwjVlszD7YXnAhUlyYUKHfc0D8oQjRx6BAgBEAQ&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FMagicRoundabout(Swindon)&psig=AOvVaw1G0K63pD90sKRkcX9JTFtc&ust=1579186288265014

People using the road make mistakes (like running stop signs and red lights), always have and always will. Crashes will always be with us, but they need not result in fatalities or serious injury. 

Modern roundabouts are the safest form of intersection in the world - the intersection type with the lowest risk of fatal or serious injury crashes - (much more so than comparable signals). Modern roundabouts require a change in speed and alter the geometry of one of the most dangerous parts of the system - intersections.  

The reduction in speed to about 20 mph and sideswipe geometry mean that, when a crash does happen at a modern roundabout, you might need a tow truck, but rarely an ambulance. Visit the Insurance Institute for Highway Safety for modern roundabout FAQs and safety facts. 

Modern Roundabouts are one of several proven road safety features (FHWA).  

The life saved may be your own.

https://safety.fhwa.dot.gov/provencountermeasures/roundabouts/ 

https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/ 

Cheddar video: https://cheddar.com/media/why-the-u-s-hates-roundabouts

Early minor crashes decrease over time:

https://www.iihs.org/news/detail/safety-at-two-lane-roundabouts-improves-over-time-new-study-shows

https://www.iihs.org/topics/bibliography/ref/2180 

https://www.thisweeknews.com/news/20190325/gahanna-cuts-roundabout-learning-curve

https://www.roads.maryland.gov/OC/25th_Anniversary_Roundabouts%20.pdf 

Glastonbury, CT: https://www.journalinquirer.com/towns/glastonbury/glastonbury-traffic-roundabouts-have-reduced-accidents/article_4b76c232-1525-11ea-af1a-e7b77a1f1b5c.html 

Butler County, OH: https://butlercountyoh.us/roundabouts-contribute-to-safety-less-crashes-in-butler-county/ 

  Modern, slow and go, roundabout intersections have less daily delay than a stop light or stop sign, especially the other 20 hours a day people aren’t driving to or from work (it’s the #2 reason they’re built). Signals take an hour of demand and restrict it to a half hour, at best only half the traffic gets to go at any one time. 'At best' because traffic signals must have the yellow and all red portion (6+ seconds per cycle) for safety, and modern roundabouts do not. At a modern roundabout, drivers entering from different directions can all enter at the same time. Don’t try that with a signalized intersection.  

https://www.lrrb.org/pdf/200824.pdf 

https://link.springer.com/article/10.1007%2Fs12205-013-0338-5 

https://www.researchgate.net/publication/311336618_Effect_of_vehicle_composition_and_delay_on_roundabout_capacity_under_mixed_traffic_conditions 

Reduced delay at intersections equals less pollution from idling cars (a local health issue; global warming too):

Emissions Study: https://www.sciencedirect.com/science/article/pii/S1361920901000116 

2014 CARB study: https://www.arb.ca.gov/cc/sb375/policies/rndabt/roundabout_brief.pdf 

Computer Modelling: https://ascelibrary.org/doi/10.1061/9780784413586.029 

Carmel, IN: https://www.euronews.com/2019/12/11/city-led-lights-how-carmel-indiana-other-u-s-cities-n1099336 

Green Intersections: https://medium.com/@jtrea81/green-infrastructure-the-forgotten-part-of-a-climate-change-agenda-a0544581aaaf

Try driving round the Arc de Triomphe in Paris. A roundabout on steroids.

Failing to use left indicator before exiting the roundabout should be a capital offence. Unless it's a German car which as we all know doesn't have them.

The scariest roundabouts are a) the Hyde Park roundabout - try doing that on a moped! And b) the vastly complex set of five roundabouts in Swindon!

Still better than traffic lights!

Roundabouts work! It's as simple as that! They stop traffic congestion, which also reduces driver frustration and recklessness, thus also reducing accidents as well. Of course there are some drivers who just don't get roundabouts. I've seen drivers going the wrong way against traffic. This is only a matter of education and familiarity to avoid these situation. Multilane roundabouts are everywhere here in Australia. Most are small, but some are a kilometer wide with many exits. I'd guess those who have trouble negotiating roundabouts are the same ones who have trouble reverse parking a car and shouldn't be on the road in the first place.

Japan has over 200,000 sets of traffic lights, which is double the amount in the USA, the next closest country statistically. Any initiative to reduce the ridiculous amount of traffic lights in Japan is a good thing.