Hi!

I'm doing roudabout simulation and wondering how
inside radius and outside radius is affecting to the simulation. Here in Finland we have roundabouts with two inner circles. The other inner circle with block pavement for the heavy-duty veghicles and the normal pavement for the passenger cars. Which inner circle radius it's better to use for to get right simulation results? In my case there is heavy-duty vehicles 10%.

Actually I'cant see any differences in simulation if I change inside radius and now I'm wondering is it supposed to affect to the simulation in SimTraffic?

I'm having a hard time picturing this...can you give an example I could see on google maps?

Hi Eric! Nice to notice someone is intrested...

Anyway you can find this kind of place for example from http://maps.live.com/ -> Matinkylä -> roundabout is at the soutpart of the Kehä II. Intersection between Nelikkotie and Gräsänlaakso. Hope you find it. Take the Bird's eye so you can see it.

There the brown inner circle is bloc pavement and heavy vehicles can use also this part.
Which inner circle radius it's better to use for to get right simulation results? Is it supposed to affect to the simulation in SimTraffic if you change the inside radius?

Thanks Heini

WOW, the bird's eye view looks really great - much more detail than google maps would have given me. neat.

OK, so what I see is a classic single lane roundabout with what I guess is a sloped, concrete "apron" (you said block, is this brick or some other textured surface?) for the trucks that will "overtrack" with their long trailers. For this I'd use the inner and outer radius of the asphalt surface itself, the apron isn't a second lane itself and so doesn't add capacity, at least, not the was they work here in the US.

Too bad that live bird's eye view picture wasn't taken a few seconds later, the bus would have told you the answer...!

Eric
Caltrans

Thanks, yes there is bricks this texture on the inner circle, and seems to work as like you say.

Do you know is there any affecting change headways and gap acceptance at the roundabout? It´s hard to see any changes if I change this parameters and I can´t simulate two simulations at the same time, because of the only one licence. Sometimes cars seems to go over aech other even if my gap acceptance is at the high level. Strange??

Well, no roundabout implementation that I've seen in a microsim model so far, is perfect.

I've not modeled many roundabouts in Synchro and so I don't know how much of a change altering the headway and gap acceptance will get you. If you're trying to run a simulation that won't show the back of one car running into another in the roundabout, I'd say don't worry about it. for one thing, all the vehicles in synchro are rectangles; the trucks won't pivot at the kingpin and double trailers won't either. (and so you won't see any overtracking) You have to be willing to accept some level of abstraction. In this case, I'd say it has to do with the car following programming, but I'll let one of the experts tell you for sure...John?

Eric

Thanks Eric about your opinions. Roundabouts are compilicated to simulate, that is fact. Now I have anyway enough good results with sigle lane roundabouts with Synchro, some imagination is anyway needed . Maybe double lane roundabouts is my future case, but that is other case that.

you might want to modify the drivers patrameters modified. that sometimes helps.