Chicago Traffic Tracker - Historical Congestion Estimates by Segment - 2018-2023

This dataset contains the historical estimated congestion for over 1,000 traffic segments, starting in approximately 2/28/2018 and ending 9/8/2023. Older records are in https://data.cityofchicago.org/d/77hq-huss. Newer records are in https://data.cityofchicago.org/d/4g9f-3jbs. The most recent estimate for each segment is in https://data.cityofchicago.org/d/n4j6-wkkf. The Chicago Traffic Tracker estimates traffic congestion on Chicago’s arterial streets (non-freeway streets) in real-time by continuously monitoring and analyzing GPS traces received from Chicago Transit Authority (CTA) buses. Two types of congestion estimates are produced every 10 minutes: 1) by Traffic Segments and 2) by Traffic Regions or Zones. Congestion estimates by traffic segments gives observed speed typically for one-half mile of a street in one direction of traffic. Traffic Segment level congestion is available for about 300 miles of principal arterials. Congestion by Traffic Region gives the average traffic condition for all arterial street segments within a region. A traffic region is comprised of two or three community areas with comparable traffic patterns. 29 regions are created to cover the entire city (except O’Hare airport area). There is much volatility in traffic segment speed. However, the congestion estimates for the traffic regions remain consistent for a relatively longer period. Most volatility in arterial speed comes from the very nature of the arterials themselves. Due to a myriad of factors, including but not limited to frequent intersections, traffic signals, transit movements, availability of alternative routes, crashes, short length of the segments, etc. Speed on individual arterial segments can fluctuate from heavily congested to no congestion and back in a few minutes. The segment speed and traffic region congestion estimates together may give a better understanding of the actual traffic conditions.

本数据集涵盖了2018年2月28日左右至2023年9月8日期间，超过1000个交通路段（Traffic Segments）的历史拥堵估算数据。旧版记录存放于https://data.cityofchicago.org/d/77hq-huss，新版记录存放于https://data.cityofchicago.org/d/4g9f-3jbs，各路段的最新拥堵估算数据则存放于https://data.cityofchicago.org/d/n4j6-wkkf。

芝加哥交通追踪器（Chicago Traffic Tracker）通过持续监测并分析来自芝加哥交通管理局（Chicago Transit Authority, CTA）巴士的GPS轨迹，实时估算芝加哥市内主干道（arterial streets，非高速公路）的交通拥堵状况。该系统每10分钟生成两类拥堵估算结果：1）按交通路段（Traffic Segments）划分的估算；2）按交通区域/分区（Traffic Regions or Zones）划分的估算。

按交通路段（Traffic Segments）的拥堵估算，通常会给出单条街道单向半英里路段的观测车速。交通路段级别的拥堵数据覆盖了约300英里的主要主干道。按交通区域的拥堵估算，则会给出某一区域内所有主干道路段的平均交通状况。每个交通区域由2至3个交通模式相近的社区区域组成，全市共设置了29个此类区域（奥黑尔机场区域除外）。

交通路段的车速波动幅度较大，但交通区域的拥堵估算结果则能在相对更长的时间内保持稳定。主干道车速的大幅波动本质上源于道路自身的特性，包括但不限于频繁的交叉口、交通信号灯、公交通行、备选路线可用性、交通事故、路段长度过短等诸多因素。单个主干道路段的车速可在数分钟内从严重拥堵切换至畅通状态，再恢复至拥堵。将路段车速与交通区域拥堵估算相结合，能够帮助人们更全面地理解实际的交通状况。