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This is the name given to build-outs added to a road to narrow it. There are various configurations of chokers, but the philosophy is to narrow a road to change its perception to drivers. When a narrowing is carried out at an intersection the term 'bulb-out' is usually used. The least intrusive choker is a narrowing on either one or both sides of the road which still permits two way traffic. The photo below illustrates one such choker.
I have used these combined with a neighborhood entry sign or structure to give definition to the entry point to a residential neighborhood to help change drivers' perceptions. I have also seen individual chokers combined with speed humps. If chokers are constructed on alternate sides of a road it will create a winding path for traffic cutting down on the tendency to speed on a straight road. I do not have any speed measurements, however, to be able to quantify the speed reduction which comes from chokers that allow two way traffic. I have constructed as a trial chokers that only allow one way traffic with the chokers being offset ['twisted choker' or chicane]. The photo shows this temporary installation, which would have been replaced with curbing if made permanent.
No priority direction was signed to accord with the philosophy that drivers need to slow down to 'negotiate' their way through with oncoming drivers. Three of the chokers were installed on approximately one third of a mile length of residential collector road about 26 ft wide carrying 3,000-4,500 vehicles per day. Speed studies approximately mid way between the chokers showed very little reduction in speeds although by observation traffic had to slow through the chicane. Contrary to what might be expected there were no reported crashes attributable to the chokers. The chokers remained in place for about 6 months but were removed because residents of the road itself did not support them. Residents cited problems with access to their property [if they lived near a choker] and stories of irate drivers getting in to confrontations when opposing drivers would not yield. The chokers were replaced with 'flat top' speed humps. My conclusion is that chokers should allow two way traffic and their main usefulness is in changing the perception of a road rather than physically changing drivers' behavior.
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