Team members: Kefan Long, Yayin Cai, Ran Xin
What is the problem?
Vision zero is gaining momentum across the world. First developed by the Sweden Transport Administration in 1995, Vision zero has quickly proven to be a successful strategy in saving lives across Europe and is now adopted by many large American cities. By January 2018, over 30 American cities have become vision zero cities, including Philadelphia.
Philadelphia introduced vision zero in 2016 and had its own vision zero action plan on September, 2017. While the city set the ultimate goal of reducing traffic-related death to zero by 2030 in the action plan, the one-year update said the city will not reach its goal if current downward trend of traffic fatality continued.
So, what is vision zero? It is a new method in the field of transportation plan. Different from traditional planning approach, vision zero targets at preventing traffic fatalities and severe injuries and regards certain human failings as forgivable. Vision zero also emphasizing the value of saving one single life at all costs.
Source: Vision Zero Network
Crash data of Philadelphia has shown that lives of pedestrians are disproportionally threatened when they are involved in crashes. They are three times more vulnerable to traffic fatality than a vehicle occupant. Besides, around half of severe crashes happened in intersections, and 47% of severe crashes happened at dark.
Source: Philadelphia VZ One Year Update
Among all vision zero plans, a generally recognized way of effectively reducing crash severity is to slow down the driving speed on the road. When the driving speed goes down from 40 Mph to 20 Mph, the fatality rate of people hit by a car reduces from 90% to 10%.
Source: Philadelphia Vision Zero Action Plan
Knowing where and when severe crashes happen in Philadelphia, and what solution is effective in preventing crashes or reducing crash severity, we decide to focus on the idea of reminding drivers in advance to slow down when pedestrians behave dangerously. Based on our crash analysis, we want our solution to detect pedestrians’ jaywalking behaviors, especially at intersections, and remind drivers when they drive close to the intersection. While part of our project also works to remind pedestrians, the main goal is sending the warning to drivers and asking them to change their behaviors. Even though asking drivers to pay for pedestrians’ misbehaviors sounds unfair, slowing down did safe life and it is proven to be effective. That’s how we devise our project, SMARTISS, a smart intersection safety system.
What is the solution? SMARTISS
SMARTISS is a “pedestrian-protective, driver-informative” system that consists of multiple add-in installations. They can be installed on street poles of intersection traffic light and crosswalk light in the intersection, as well as mid-block pole where drivers can see before they drive through the intersection.
The intersection installations can detect whether pedestrians are running the red light, and respond to pedestrians’ misbehavior by our smart LED notice as well as speaker warning. Smart LED is a ring-shaped LED light with inner notice signs. The content of signs may differ, like “SLOW” on the traffic side and “WATCH FOR VEHICLE” on the crosswalk side. Once pedestrians are found jaywalking, smart LED on the crosswalk turns on to remind pedestrians, while smart LED on the roads turns on to remind drivers. Also, pedestrians will receive the warning from the speaker, like “Stop Crossing” or “Be Careful”.
Sometimes, it is hard for drivers to recognize the position of a jaywalking pedestrian during the night. Therefore, SMARTISS also includes a lighting system that projects light or signs on the roads. The lighting system only works at night. Once the system is triggered, it will shine lights on the road, which helps drivers to see pedestrians clearly.
Compared with traditional approaches that deal with jaywalking behavior and intersection safety on pedestrian side, SMARTISS puts more emphasis on alerting drivers, which reflects the concept of imperfect pedestrians in vision zero. SMARTISS has the advantage of combined reminding system, which includes audio warning and Smart LED. The additional lighting system enable SMARTISS to deal with jaywalking during the night. Besides, although SMARTISS is powered by street pole electricity, it works separately and doesn’t influence current traffic lighting.
Where to implement?
Before promoting SMARTISS across the city, we want to start with a pilot project. We classify the intersections in Philadelphia based on two criteria: whether it is busy-traffic, and whether it is dangerous. The first is defined by AADT, which refers to annual average daily traffic, and the second is defined by number of crashes during 2013 to 2017 that involve at least one pedestrian and have the indicator of intersection crash marked as yes. Philadelphia should prioritize intersections that are both busy-traffic and dangerous.
By combining two criteria together, 40 intersections became our first SMARTISS candidates. Besides traffic volume and crashes, we also want to locate the pilot project at a secondary or tertiary road so that it is easier to observe the effects with least effort in engineering.
Finally, we decide to implement the pilot project at 34th & Market street. It only takes 5 minutes to walk from University of Pennsylvania and Drexel University. And it is close to a subway station, which provide a constant flow of pedestrians. Also, the downhill on the north side of the intersection makes it harder for the vehicles to slow down. In addition, the parking lane blocks drivers’ view when it is full of cars, especially at night.
The following picture demonstrates how we implement the program at 34th & Market Street. When jaywalking behavior is detected in the intersection, the signal will immediately be sent to intersection pedestrian reminder through wire connection. The signal will also be sent to intersection automobile reminder and mid-block automobile reminder through radio transmitter.
The intersection pedestrian reminder will turn the smart LED on and play the warning message to pedestrians after receiving the signal. Also, additional lighting system will project light or notice to light the crosswalk and get drivers noticed the position of jaywalking pedestrians (as you can see, “careful” is projected on the road). After receiving the signal from radio receiver, the automobile reminders in both intersection and mid-block will turn on smart LED to remind drivers who are waiting on the intersection or are driving close to the intersection.
How does SMARTISS work?
SMARTISS is a traffic signal system add-in, powered by the traffic signal system, and can read the traffic signal. It will be triggered ONLY when the crosswalk traffic light is red when pedestrians are not allowed to cross the street.
I. Sensors
SMARTISS uses 3 sensors to detect different scenarios of jaywalking pedestrians:
- Ultrasonic distance sensor: detects any object within the distance range which is 60-120 cm.
- Passive Infrared (PIR) sensor: detects any object emits infrared light. PIR sensor is important to distinguish if a subject is a person or something else.
*Distance and PIR work together to detect the presence of pedestrians in a given distance and direction.
- Photo resistor: senses the environment light intensity, and detects whether it is during the day or at night.
II. Response
When SMARTISS is triggered (sensors successfully detect jaywalking pedestrians), it will respond to drivers and pedestrians by:
- Smart LED
- The Smart LED on both intersection and mid-block will be on.
- Smart LED is designed to remind both drivers and pedestrians.
- The content of notice in the smart LED differs at crosswalk and traffic side.
- Audio warning
- The speaker will start playing warning message.
- The messages are different based on different scenarios.
- Its volume goes down at night to avoid neighborhood disturbance and avoid frightening pedestrians.
- Lighting system
- It only works at night and is additionally controlled by a photo resistor.
- Once the SMARTISS is triggered, the lighting system starts working.
- Lighting system is designed to remind drivers.
The following diagram demonstrate how different parts work together：
III. Two scenarios
In details, we further developed 2 scenarios for jaywalking:
Scenario 1
During the red light time, in the first 5 seconds, only PIR sensor works to detect people on the crosswalk, and will be responded by the smart LED and sound “Be Careful”.
- This scenario makes sense when a pedestrian legally crosses the street at the beginning, but maybe at the street center, the crosswalk light turns to red.
Scenario 2
After the first 5 seconds during the red light time, both distance sensor and PIR sensor will work together to detect the presence of pedestrians, and then it will be responded by both smart LED again and a new sound notice “Stop Crossing” to warn pedestrian about their misbehavior.
**But no matter which scenario, once SMARTISS is triggered, it will delay for additional 5 seconds even though a pedestrian has already crossed the streets.**
IV. Wireless Communication
Sensors on the crosswalk send jaywalking signals to intersection automobile reminder and mid-block automobile reminder by radio transmitter/receiver kit. The transmitter delivers the state of crosswalk out and receivers that catch the jaywalking signal turn on smart LED immediately (the delay is less than 0.1 s in our test). Therefore, different parts of SMARTISS can communicate wirelessly and efficiently through radio communication. It also enables the mid-block automobile reminder to be placed in different locations.
To make sure that drivers get noticed on time, the position of mid-block reminder can change according to speed limit of the streets and corresponding brake distances. Since most city streets in Philadelphia have a speed limit of no more than 40Mph, the mid-block reminder can change from 12 meters to 36 meters, which is still within the range of radio transmitter/receiver communication.
V. Video
What are the costs and benefits?
As is show in the table on the left, the estimate cost of installing SMARTISS on one side of the road is around $750 – $1,000. If we install two at one intersection, the total cost is around $1,500 – $2,000. The most complicated intersection will cost no more than $12,000 based on our investigation of all 40 dangerous intersections.
Apart from 34th & Market street, we are considering promoting SMARTISS among all other 39 intersections in the next step. From 2013 to 2017, 293 pedestrian involved crashes took place at these intersections, as shown on the map on the right. We estimate the cost of promoting these measures among all 40 intersections. If 20% of drivers notice the lighted signs and slow down, then hopefully we are expecting to prevent 12 crashes or reduce their severity. The higher proportion of drivers get noticed and change their behaviors, the more life and injuries of pedestrians and drivers will be saved from these crashes. Compared the relatively low cost of installation and maintenance, SMARTISS is rewarding and creates a safer Philadelphia for all pedestrians and drivers. This is what vision zero addresses.
What to do next?
We consider how SMARTISS could contribute to Philadelphia if more and more intersections have SMARTISS installed. Currently there are two possible ways. First, we can add a cellular module and use SMARTISS to sense and send real-time violations to the PPD (Philadelphia Police Department), so that PPD could prioritize police power more easily. We can also add a storage device and use SMARTISS to sense and store violation data. The city can collect the periodical data, or SMARTISS could also send periodical data to the city through additional cellular module. The data can be used as an important way of evaluating intersection safety and help city and planning commission to prioritize their budget and projects in Vision Zero and transportation plans.
Appendix
- The code for our prototype
- The parts in we use in our device:
- For tutorials, you are welcome to refer to:
Ran Xin: PIR sensor
Yayin Cai: SmartLED
Kefan Long: Transmitter and receiver