Secured NYC-What we do?
Author: Jiabao Sun and Hanbo Lei
Abstract
This project aims to explore the features which impact traffic safety, namely traffic flows, street width, and three Vision Zero strategies. First, this article provides a brief introduction of 2014 New York City Vision Zero background and our research scope. Then, the method and data of this study is explained with details. After that, several findings are illustrated: Vision Zero program strategies can reduce the traffic accidents while traffic flow and street width impact little on traffic accidents.
1 Introduction
New York City, the most populous and densely populated city in the United State, has a 2020 population of 8,804,190 distributed over 300.46 square miles (778.2 km2) (Wikipedia 2022). With so many people living in and working in New York City, safety is always a top concern of citizens, especially traffic safety is a major issue in New York City with people advocating for more walkable streets and better streets environment. Today in New York, approximately 3,000 New Yorkers are seriously injured and more than 200 are killed each year in traffic crashes. Being struck by a vehicle is the leading cause of injury-related death for children under 14, and the second leading cause for seniors (New York City Government 2022).
Therefore, many suggestions are put forward to mitigate traffic crashes. One common suggestion is managing traffic volume to avoid accidents (Retallack 2020, Martin 2002). Others recommend that narrower streets help promote slower driving speeds which, in turn, reduce the severity of crashes (Lane Width nd.). In addition to the idea indicating the relationship between physical features of streets and traffic crashes, NYC established the Vision Zero initiative to reduce avoidable accidents and injuries through expanded enforcement, better street design and configuration, and broad public outreach and communications in 2014. Hence, it is necessary to study the spatial distribution of traffic injuries numbers, and how streets’ physical features or 2014 Vision Zero impacted the overall traffic status in New York City. Based on the reactions of different independent variables, future policy and urban planning as well as design suggestions are provided.
The research scope of this study focuses on Manhattan because Manhattan includes a large proportion of traffic in NYC, and one borough allows visualization to be clearer. Although both traffic injuries and traffic fatalities are supposed to be mitigated, we focus on the effect on traffic injuries in order to avoid incidental.
2 Methodology
2.1 Research Question
How effective Vision Zero strategies are?
Are there features that contribute to the improvement of traffic?
2.2 Data
Street Network:
NYC Street Centerline, 2022, Department of Information Technology & Telecommunications, https://data.cityofnewyork.us/City-Government/NYC-Street-Centerline-CSCL-/exjm-f27b
NYC LION, 2022, Department of City Planning, https://data.cityofnewyork.us/City-Government/LION/2v4z-66xt
Traffic Data:
Motor Vehicle Collisions, 2013–2021, NYC Police Department. https://data.cityofnewyork.us/Public-Safety/Motor-Vehicle-Collisions-Crashes/h9gi-nx95
Automated Traffic Volume Counts, 2011–2021, Department of Transportation, https://data.cityofnewyork.us/Transportation/Automated-Traffic-Volume-Counts/7ym2-wayt
Vision Zero program:
VZV Speed Humps, 2018, Department of Transportation, https://data.cityofnewyork.us/Transportation/VZV_Speed-Humps/7f9e-jic4
VZV Street Improvement Projects intersections, 2018, Department of Transportation, https://data.cityofnewyork.us/Transportation/VZV_Street-Improvement-Projects-SIPs-intersections/79sh-heg3
VZV Arterial Slow Zones, 2018, Department of Transportation, https://data.cityofnewyork.us/Transportation/VZV_Arterial-Slow-Zones/ixwf-56db
2.3 Variables
In order to combine the design elements of streets into our study, we test the correlation between traffic flow and accidents (injured and killed cases) as well as the correlation between street width and accidents. Here the OLS regression model is adopted for mainly two reasons: first is that it is the most common method for fitting a regression line which allows to calculate the best fitting line over the observed data; second is that the criteria for this regression model are to minimize the sum of the squared errors. As for the interpretation of the result, if p value is lower than 0.05, then the author deems that the x variable has significant positive/negative influence on the y variable, which also means that the correlation between x variable and y variable is significant.
2.3.1 Traffic Flow
Based on the OLS regression result, there is no overall correlation between traffic flow and accidents (injured cases and killed cases). This means that from an angle of the whole New York City, we can not identify a clear negative or positive connection between flow of traffic and traffic accidents numbers. But here it is worth noticing that we need to admit that there is the possibility that in some areas or neighborhoods, there can be significant relationships which need further exploration. Also, as is shown in the figure 2 above, the traffic flow data is not complete with all streets included.
2.3.2 Street Width
As for the regression result of the street width, there is a relatively better connection between street width and traffic accidents than the connection between street flow and traffic accidents, but still the relationship is not significant. This shows that in New York City, the number of traffic cases is seldom influenced by the street width.
Because above street flow and width are rarely correlated with traffic accidents for New York City as a whole, we focus more on the strategies that Vision Zero used to improve the overall safety.
2.3.3 Vision Zero Strategies
To quantify the effect of the Vision Zero program, Figure 5 visualizes how the change of injuries number after 2014’s Vision Zero Plan implementation based on segments of streets. From the figure, yellow or red “increased” streets are a little bit more than green “decreased” streets. From the statistics, the average annual injuries on all streets increase 4.68%, from 0.40 to 0.42.
Since the Visions Zero program is a plan that includes many policies and actions, such an increase cannot prove the failure of the whole Vision Zero. As we know, the purpose of a program is realized by actions. We focus on the effect of individual actions in the Vision Zero program by comparing the change in percentage of injuries after 2014 between the streets with or without Vision Zero action implementation. There are 3 actions, speed humps, Street Improvement Projects intersections, and Arterial Slow Zones, which might influence the injuries of streets directly. Speed humps are raised to reduce vehicle speeds and drivers’ attention. The Arterial Slow Zone program uses a combination of a lower speed limit, signal timing changes, distinctive signs and increased enforcement to improve traffic safety. Street Improvement Projects use multiple treatments (signals, markings, concrete etc) on both corridors and intersections to better organize traffic, improve travel times, create shorter, safer pedestrian crossings, and safe routes for bicycle travel.
From table 1, all streets that implemented these actions have higher annual injuries on streets, which means programs are implemented on more dangerous streets. To ensure whether the 3 actions of Vision Zero work out, we compare the average annual injuries before and after the Vision Zero program based on the implementation situation of each action. When injuries in streets without such actions increase about 5–6%, the Street Improvement Projects and Speed Humps decrease by approximately 3% injuries after implementing Vision Zero. The Arterial Slow Zones can curb the increase rate to 1.4% instead of 5%, even if it fails to decrease the annual injuries rate. Thus, these 3 actions of Vision Zero effectively improve traffic safety.
3 Conclusion
Horizontal streets tend to have more accidents and injuries than vertical avenues. Also, the high injured cases concentrate in the lower and middle part of Manhattan, the upper west of Manhattan, and the north part of Brooklyn. One potential guess about why there are more accidents in streets than avenues is that normally streets are longer, which makes the visual distance range smaller and the reaction time to sudden movements longer.
As for the trend of Manhattan, the injured cases in Manhattan concentrated in the middle west side and Harlem area. There are spatially separate spots of high injured cases in lower Manhattan near the Wall Street region.
Since the regression analysis above shows very little correlation of street flow and width, here we mainly focus on the exploration of street improvement projects intersections, streets in arterial slow zones, streets with speed humps. Although there is a group of people claiming that the number of injuries and death has increased, it can be ascribed to the impact of the overall environment but not the failure of the Vision Zero methods. Based on our study results, in fact, some Vision Zero methods are useful and need further attention and expansion in implementation.
Here lists our recommended implementation location in Manhattan. Figure 8, 9, 10 demonstrates the streets interacted with these actions and how annual injuries change after Vision Zero.
Speed Humps help streets in Harlem decrease their annual injuries. Street Improvement Projects intersections have covered many areas with high street injuries in the lower middle west, and decreased injuries there. Arterial Slow Zone on Park avenue works well in horizontal streets.
Since these 3 actions work well, they could be implemented broadly. As figure 8 shows, there are many injuries in the lower middle west without speed Humps. We recommend more Speed Humps should be installed there. More Street Improvement Projects intersections should be implemented in Harlem. Arterial Slow Zone might reduce more injuries if it extends south to lower Manhattan.
4 New Data
Besides the injuries and injuries change after Vision Zero, street width, and traffic volume, our team also visualizes the hourly injuries or death number on streets. The grasshopper file and a visualization are shown below, which will be submitted to final project google drive.
5 Summary
Designers should not pay attention to manage traffic flow or road width to reduce traffic injuries due to their little effect on traffic injuries. But Vision Zero is a worthy attempt. Because even though the total number of traffic injuries has increased since 2014, there are specific actions that can still reduce traffic injuries, three of which were verified in this research. These effective actions should be implemented more on New York’s most high-crash streets.
6 Bibliography
Lane Width. National Association of City Transportation Officials. https://nacto.org/publication/urban-street-design-guide/street-design-elements/lane-width/#:~:text=Narrower%20streets%20help%20promote%20slower,less%20construction%20material%20to%20build.
Martin, Jean-Louis. “Relationship between crash rate and hourly traffic flow on interurban motorways.” Accident Analysis & Prevention 34, no. 5 (2002): 619–629.
New York City Government. “ Vision Zero in New York City”. New York City Government official website, 2022, https://www1.nyc.gov/content/visionzero/pages/
Retallack, Angus Eugene, and Bertram Ostendorf. “Relationship between traffic volume and accident frequency at intersections.” International journal of environmental research and public health 17, no. 4 (2020): 1393.
Wikipedia. “New York City”. Wikipedia, March 2022, https://en.wikipedia.org/wiki/New_York_City
