TditilTraditional ItIntersecti ons vs. Roundabout Intersections
Most people are familiar with roundabout concepts, but may not be accustomed to diidriving thhhrough them. Roundabouts have proven to be a safe alterna tive to sttddandard itinstersec tions.
Traditional Intersection
Traditional iiintersection signal cycle has 4 phases –
2 for left turns
2 for through movements Traditional Intersection
4 Phase Signal Cycle Times*
10% 6%
22% 62% lefts straight through
*average intersection
75% of the traffic (through movement) gets only about 60% of the cycle time Too much time spent on left turns and yellow signals (transition between movements)
Roundabout Intersection
Intersections with stop signs, whether 4‐way or 2‐way also have some delay for cars moving through them A roundabout is quite different in that all legs/approaches to the intersection can be treated equally –all vehicles “turn right” • All vehicles slow down to enter the roundabout • When other vehicles are in the roundabout, there is some delay to enter • No delay to exit No two roundabouts are alike – they are designed for the specifics at the intersection Left turns are restricted near roundabouts, like this one in Las Vegas. Drivers proceed around the roundabout and return to their destination.
Access Management
Driver Destination
Access management includes the use of medians, turning lanes, turn arounds/roundabouts, and consolidated driveways to increase safety and improve roadway function. It is very important to manage access near roundabouts. Drivers should proceed around the roundabout and return to destination instead of making a left turn. Access Management
Driver Destination
Access management includes the use of medians, turning lanes, turn arounds/roundabouts, and consolidated driveways to increase safety and improve roadway function. It is very important to manage access near roundabouts. Drivers should proceed around the roundabout and return to destination instead of making a left turn.
Roundabouts, and roundabout features, are used as part of other innovative intersections like bowties and hamburgers. Bowtie Intersection
Bowtie intersections use two roundabouts, Bowtie intersections set in a crosstreet can accommodate away from the main more vehic les per hour intersection,
to accommodate llfeft turns and allow more traffic than a single roundabout to flow smoothly through or a standard intersection. the main intersection.
Hamburger Intersection
Hamburgers, or Everett, MA “through‐about” intersections, also use roundabout ftfeatures to manage turning movements at key intersections. Hamburger Intersection
Hamburger intersections have been built in several locations in the eastern US and in Mexico: o Everett, MA –Revere Beach Pkwy & Mystic View Rd o Fairfax, VA – Arlington Blvd & Lee Hwy o Cherry Hill, NJ – Kaighns Ave & Church Rd o Marlton, NJ –Route 73 & Marlton Pike o Saltillo, MX – Blvd Los Fundadores & Blvd Morelos o Tijuana, MX – Cuauhtemoc &Paseo Centenario Tijuana (near Rio Tijuana shopping mall) and several are in the Playas de Tijuana//dJardines ddlel Sol neighbor hoo d
Roundabouts in Urban Form
Las Vegas, NV In some cases, Summerlin Village Center Circle roundabouts are much more than just intersections ‐ they have become part of the urban form and the neighborhood pattern. Roundabouts in Urban Form In some cases, roundabouts are much more than just intersections ‐ they have become part of the urban form and the neighborhood pattern. Paris, France Place de l’Etoile
Roundabout Intersection
Good potential for aesthetic improvements with landscaping, public art, etc. In many cases uses roughly the same amount of right‐of‐way as standard intersection No signals needed for traffic control, but pedestrian crossing signals may be desired
Thank You
For more information visit compassidaho.org Air photos sources include Google Earth, COMPASS, and Clark County