Date:    Mon, 21 Dec 2009 16:24:24 -0800

From:    Lee Rodegerdts <LRODEGERDTS@KITTELSON.COM>

Subject: Re: Can you help us find data on driver gap acceptance?

Two NCHRP studies have formed the basis for the procedures in the

Highway Capacity Manual: NCHRP 3-46 for TWSC intersections, and NCHRP

3-65 (NCHRP Report 572) for roundabouts. Both used the same technique of

recording events and a maximum likelihood method for estimating critical

headway (formerly critical gap) and follow-up time. The resulting

equations link capacity to conflicting flow and, in the case of TWSC

intersections, the impeding effects of higher ranking movements.

Lee Rodegerdts

Kittelson & Associates, Inc.

lrodegerdts@kittelson.com 

From: Roundabout Research [mailto:ROUNDABOUTS@LISTSERV.KSU.EDU] On Behalf

> Of Dona Sauerburger

> Sent: Monday, December 21, 2009 11:58 AM

> To: ROUNDABOUTS@LISTSERV.KSU.EDU

> Subject: Can you help us find data on driver gap acceptance?

>

> Hi everyone!  Many of you are extremely knowledgable about driver behavior

> at intersections, so I'm hoping you can help us out.

>

> A group of us are testing a street-crossing strategy that is being taught

> to

> blind pedestrians.  The strategy assumes that it is safe for pedestrians

> to

> cross a street with no traffic control whenever it is crossed by a driver

> who was waiting at the stop sign of the intersecting street.

>

> Can any of you steer us to studies of drivers' gap acceptance at

> situations

> such as entering or crossing a street with no traffic control, or entering

> roundabouts, or even turning left across oncoming traffic at a signal?

>

> In particular we'd like to know whether the length of the gap that drivers

> accept is related to anything that can be observed / measured, such as

> traffic volume and/or length and frequency of gaps in traffic that they

> are

> trying to cross or enter and if so, how closely is the behavior related to

> it.

>

> Knowing how well the observable features of the street and traffic can

> predict drivers' gap acceptance will help us know how well we can rely on

> an

> individual driver's behavior to determine if there is a gap long enough to

> cross.  If idiosynchracies of the drivers (such as driver's age or risk

> acceptance, etc.) are a major factor in their behavior, then we shouldn't

> assume anything about the length of a gap based on a driver's acceptance

> of

> it.

>

> Thanks!

>

> -- Dona

> _________________________________________________

> Dona Sauerburger, COMS

> 1606 Huntcliff Way, Gambrills, Maryland 21054

> sauerburger@mindspring.com

> 301-858-0138