I missed last Thursday’s STAT W4701 class due to being under the weather but was able to check it out via Columbia Video Network. Dr. Malecki posted a mini assignment where we could use NYC Crash Data. I’ve used this data before for mapping pedestrian and bicycle injuries and fatalities. This data used to be available via Transportation Alternatives: CrashStat but is now delivered via NYC Open Data.

Some Python Pandas in IPython Notebook

Converted to Markdown (of course). See my old blog post Using IPython Notebook with Pandas and exporting to Markdown.

Importing and cleaning the CSV

import pandas as pd

#csv_path = 'https://raw.githubusercontent.com/nygeog/data/master/nyc_crashes/data/NYPD_Motor_Vehicle_Collisions.csv'
inCSV = 'data/NYPD_Motor_Vehicle_Collisions.csv'
ouCSV = 'data/nypd_mv_collisions.csv'

df = pd.read_csv(inCSV).rename(columns=lambda x: x.lower())

#drop ones w/out valid lat #super lazy, just grabbing lat's above 35
df = df[(df.latitude > 35)]
#print df.dtypes 
print len(df.index)

449644 #count of valid lat's records 

The original CSV data (first 5 records)

date time borough zip code latitude longitude location on street name cross street name off street name ... contributing factor vehicle 2 contributing factor vehicle 3 contributing factor vehicle 4 contributing factor vehicle 5 unique key vehicle type code 1 vehicle type code 2 vehicle type code 3 vehicle type code 4 vehicle type code 5
1 02/13/2015 21:45 MANHATTAN 10002 40.715622 -73.994275 (40.7156221, -73.9942752) FORSYTH STREET CANAL STREET NaN ... NaN NaN NaN NaN 3168577 PASSENGER VEHICLE UNKNOWN NaN NaN NaN
2 02/13/2015 21:45 MANHATTAN 10001 40.747535 -73.988307 (40.7475349, -73.9883068) WEST 31 STREET BROADWAY NaN ... Fatigued/Drowsy NaN NaN NaN 3169163 TAXI TAXI NaN NaN NaN
3 02/13/2015 21:45 BRONX 10462 40.833558 -73.857732 (40.8335582, -73.8577325) WESTCHESTER AVENUE PUGSLEY AVENUE NaN ... Unspecified NaN NaN NaN 3169251 PASSENGER VEHICLE SPORT UTILITY / STATION WAGON NaN NaN NaN
4 02/13/2015 21:44 MANHATTAN 10017 40.748800 -73.969846 (40.7487997, -73.969846) EAST 42 STREET 1 AVENUE NaN ... Other Vehicular NaN NaN NaN 3169176 PASSENGER VEHICLE PASSENGER VEHICLE NaN NaN NaN
5 02/13/2015 21:40 STATEN ISLAND 10304 40.617295 -74.080479 (40.6172954, -74.0804791) PARK HILL AVENUE OSGOOD AVENUE NaN ... Unspecified NaN NaN NaN 3169614 PASSENGER VEHICLE PASSENGER VEHICLE NaN NaN NaN

5 rows × 29 columns

Mergin’ the date (day) and time (hours)

#create datetime http://stackoverflow.com/questions/17978092/combine-date-and-time-columns-using-python-pandas
df['datetime'] = pd.to_datetime(df['date'] + ' ' + df['time'])

df = df[['datetime','latitude','longitude']]
df = df[(df.datetime > '2014-01-01 00:00:01')] #query out only data from 2014 onward
df = df.sort('datetime')
print len(df.index)

192324 #count of records 2014+


Clean and small data to import to CartoDB

datetime latitude longitude
228854 2014-01-01 00:01:00 40.725432 -73.996771
228850 2014-01-01 00:01:00 40.767889 -73.981512
228855 2014-01-01 00:01:00 40.750844 -73.978608
229144 2014-01-01 00:15:00 40.588646 -73.992452
228849 2014-01-01 00:20:00 40.689019 -73.986157

The table on CartoDB’s PostGIS Server

IPython Notebook to Markdown

IPython nbconvert 01-read-crash-data.ipynb --to markdown

Maps in CartoDB

PostGIS SQL Statement to grab 2014 from the 2014-2015/02/13 Table

SELECT * FROM nypd_mv_collisions_2014_20150213 WHERE datetime BETWEEN '2014-01-01 00:00:00' and '2015-01-01 00:00:00'

Density Hex Bins of 2014 Collisions

I’m not totally sure if when creating the classes if it ignores hex bins with no collisions or what. Need to look into that.

Density of 2014 Collisions over time (using Torque)

Animation of Density of Collisions. I think these are Kernel Densities but not sure, need to check CartoDB documentation.

Valentine’s Day 2014 Collisions (Clickbait)

I hate Clickbait. :)

Parting Note:

While informative, crash data doesn’t really tell us anything interesting about street design and whether specific places are more prone to crashes as without a denominator (such as traffic and/or pedestrian and/or cyclists) its difficult to discern if there’s just more targets for collisions (like counting homicides vs. homicides per 10,000 people) or if street design (or in the case of homicides, higher homicide rate) is actually to blame.

New York City has some traffic estimates but nothing we can attribute to every street over the whole city. There may be something that NYC DOT or someone else has, but until its FOIL’ed we can’t really create that denominator without more reliable data.