Comparing and Contrasting the Benefits of a Single Point Urban

Interchange (SPUI) With Pedestrians Against a Diamond Interchange With Pedestrians in

Terms of Safety

Elliad Dagan

The purpose of this study is to find which interchange is safer for pedestrians, the Single Point Urban Interchange, or the Small Diamond Interchange by comparing the total number of backed up cars at the Trumbull SPUI, and the Bridgeport SDI. The two different interchanges were studied based on how many cars were backed up per cycle. (40s). Every cycle of backed up cars was recorded, and on every fifth cycle the pedestrian walk button was pushed extending it to (60s) .Results thus far show that the SPUI may not be as safe as expected for pedestrians because of the increased amount of cars backed up when the pedestrian button was pushed. When the pedestrian button was pushed the entire interchange closed, except for right turn-offs, so the number of backed-up cars was greatly increased. Observations from the SDI will be compared to those of the SPUI by statistical analysis.

Abstract

For many years the Diamond Interchange has been the urban interchange of choice due to its small size and convenience.

Conversely, the more recent interchange called a SPUI is taking over because it is smaller, more efficient, and on paper safer because of less collision points.

Yet, on the road, drivers become confused by the SPUI and that may lead to more danger than a Small Diamond.

Background

Single Point Urban Interchange(SPUI)

Small Diamond Interchange

The purpose of this experiment is to discover whether or not in reality, the SPUI is safer than a Diamond Interchange when there are pedestrians at the interchange.

It is hypothesized that the SPUI will not be safer because the entire interchange closes down when the pedestrian button is pushed, causing increased car back ups.

Purpose and Hypothesis

The independent variable is the type of interchange.

The dependent variable is the amount of cars backed up on the red light cycle.

The control is the average number of cars backed up without the button pushed.

Variables and Control

A SPUI with pedestrian capabilities. A SDI with pedestrian capabilities. A pen. Laboratory notebook. Data collection tables. Permission to count cars.

Materials

The methods for this experiment would be to: Gather all of the materials Go to SPUI Count and record the number of cars backed

up per cycle for twenty cycles. Push the pedestrian walk button on every fifth

cycle. Repeat steps two through four two more

times. Go to SDI Repeat steps three through five.

Methods

Data For SPUI

https://spreadsheets.google.com/ccc?key=0ApLOwwBb1lYpdGNNYkhTNFNaRWoyOTZvV2lsY3Ixd0E&hl=en#gid=0

Data For SDI

https://spreadsheets.google.com/ccc?key=0ApLOwwBb1lYpdGtRWk9JTFhhNGF4dFZ5ZHRiTzNNUUE&hl=en#gid=0

SDI

Average w/ 42.5833333

Average w/o37.8125

Results

SPUI

Average w/

45.5

Average w/o

37.6875

The SPUI had a 7.81 increase of backed up cars with the button pushed.

The SDI had a 4.77 increase of backed up cars with the button pushed.

While the difference is not that great it is just enough to create traffic to back up into the highway. (45 car limit)

Conclusion

SPUIs as they are can be dangerous for drivers in pedestrian areas.

Simple solution: have SPUIs in areas with minimal pedestrians.

In areas with pedestrians, create on elongated off-ramp onto the SPUI

Implications

There may have been some errors with number of overall cars in the area due to time of month.

There may have been less cars in certain areas due to weather implications.

To fix these errors I could try and have several trials instead of just three.

Validity

Comparing the numbers of backed up cars in Rush Hour compared to other times.

SPUI is meant to be used for mostly rush hour.

Would use the same SPUI and same mentor.

Future Work

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