This was done using a specialized program to extract specific parameters from each of the output files generated by VISSIM.
These output parameters provided the basis for statistical analysis and subsequent predictive model development. The differences were in the ranges of 20 to 25 percent, 25 to 30 percent, and 25 to 40 percent, respectively. The NJJIs always had a higher number of stops per vehicle compared to conventional intersections, except during saturated traffic conditions where the NJJIs performed better than conventional intersections.
The capacity of the NJJI decreases as the ramp offsets decrease. Reducing the minor road offsets and major road offsets from meters to 70 meters ft to ft resulted in a reduction in the left-turn capacity on the major road approach by approximately 30 percent. The alternative signal phasing with protected left-turn phasing on the minor approach reduced the major road capacity by 20 percent, increasing the minor road capacity by 30 percent and resulting in a net 10 percent decrease in the total serviced flow for all the NJJI configurations.
The changing of the left-turn maneuver forward jughandle ramp to a right-turn maneuver reverse jughandle ramp yields a 5 to 15 percent increase in intersection capacity based on the distribution of turning movement percentages on all of the intersection approaches.
Simulation cases with three through lanes per approach on the major road, proportional increases in entering volumes for NJJIs, and conventional intersections resulted in very similar traffic performance as in cases with two lanes per approach on the major road.
The researchers developed statistical models that estimated three variables of interest commonly used by practitioners in assessing intersection traffic performance.
After several trials and iterations of different variables and model forms, the researchers developed the coefficients of the variables, which are given in table 1 for predicting average control delay CD , in seconds per vehicle, average number of stops ST , in stops per vehicle, and maximum queue MQ in feet.
The section called "Cases Modeled" provides traffic flow ranges for the statistical models. All variables are significant beyond the 95 percent confidence level. Goodness-of-fit measures in terms of the conventional R-squared statistic are strong for all models. Although the regression is based on a nonlinear model, the R-squared statistic is acceptable, according to Kvalseth 4 , when very few outliers are present.
Although the results and conclusions apply specifically to the selected geometric dimensions and traffic characteristics in cases A, B, and C, generalizations can be made for NJJIs as an intersection type.
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Introduction High-volume intersections especially during peak hours pose a particularly difficult challenge to traffic engineers and planners interested in reducing delays and improving safety for motorists and pedestrians. Type A—Forward Ramps With forward ramps, all turning traffic right and left exit onto a jughandle ramp to the right, upstream of the intersection.
Type B—U-Turn Ramps With U-turn ramps, where there is no intersection, ramps along the mainline enable vehicles to make U turns safely. Type C—Reverse Ramp With reverse ramps, left-turning traffic uses the rightmost lane downstream of the intersection into a loop ramp. The six primary factors that influence the capacity of NJJIs to accommodate what would have been left-turning vehicles from the major road are: The length of the storage capacity on the minor road in terms of the distance between the intersection and the terminus of the jughandle ramp on the minor road.
Relative proportions of through and right-turning vehicles on the major road. The volume of traffic on the minor road approaching the intersection, which affects the gaps available for left-turning vehicles from the major road ramp. Right-turning traffic from the major road may be in the same queue at the minor road as is left-turning traffic from the major road not applicable for reverse jughandle ramps.
Approach characteristics on the minor road, specifically, lane geometry and the posted speed limit. Sight distance available at the terminus of the jughandle ramp. Cases Modeled The researchers modeled the following three cases: Case A, which included a four-legged intersection with two forward jughandle ramps on the major road. Case B, which included a four-legged intersection with two reverse jughandle ramps on the major road.
Case C, which included a four-legged intersection with a forward jughandle ramp in one direction and a reverse jughandle ramp in the opposite direction on the major road. The common elements for the three geometric design configurations were: The jughandle ramp has only one lane. The forward jughandle ramp terminus widens to permit two lanes at its intersection with the crossroad. They were first constructed to help traffic flow by having a lane that allowed drivers who were exiting to remove themselves from the faster-travelling lanes for continuing travel.
These days, opponents of the system say that the disadvantages mainly confusion outweigh the intended advantages. Since the turns are foreign to drivers from so many other states, and New Jersey is frequented by drivers from so many other states, it actually may have the opposite of the intended effect as drivers have to slow down to figure the signals out or veer over two lanes at the last second.
State Senators are reportedly going to hear testimony from the DOT and make a decision whether to proceed with a vote on the bill. Have you ever missed your turn and had to go a mile out of your way in order to pull a u-turn? Have you ever got into a car accident from someone trying to catch a left turn at the last second? Here, the ramp shows up allowing for a little loop to follow around to the right.
You will merge with the original cross street at the intersection, wait at a light, cross over and then make your left to go back to the place you passed that you wanted to go to in the first place.
Sure we could have left-hand turns. There is no mastering involved. Just follow the signs. Jason Didner , a Montclair native, understands the point of them but still finds them frustrating.
So much so he turned his jughandle driving experience into a song. Become part of the Best of NJ community and get new restaurant updates, entertainment picks, and upcoming event details delivered straight to your inbox weekly! Sign in. Forgot your password? Get help.
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