Posted by: wesleyjohnston | December 16, 2015

Northern Ireland Traffic Figures – in Google Earth format!

If you just came here for the KML file, here it is! But read on…

TransportNI have just released their 2014 Annual Traffic Census report. This document is basically a huge, 140 page, list of tables, the bulk of which list the traffic counts measured at the 350 or so automated traffic counters located around Northern Ireland, for example:

Screen Shot 2015-12-16 at 20.55.25

Another table lists the locations of these counters in Irish Grid format. For example:

Screen Shot 2015-12-16 at 20.55.05

We’ve probably all seen temporary traffic counters in operation – two cables strung across the road with a box at one end. What most people don’t notice, however, are automated counters because these are buried under ground and use induction to detect traffic. But you can see the telltale pattern in the tarmac if you know where to look and you might also see the little counter box discretely located beside them.

The traffic census information is incredibly useful, because it allows us to see not only the annual average daily traffic (AADT) at each spot, but also the hourly flow during the busiest hour in the morning and afternoon peak, a more critical figure when analysing congestion. A few counters are also able to distinguish HGVs from other vehicles and give a percentage of traffic that consists of HGVs. Some can even distinguish traffic types in even more detail than this.

However, while the Report does have maps at the back, it is still cumbersome to use because you have to find the locations you want in the maps at the rear and then refer back to the various tables in the rest of the document.

So what I’ve done is to re-package some of this material in KML format (download here), which means that you can open it in Google Earth and see the data on an actual map. The information I have included is: the counter name and number, AADT figure for 2014, the morning and evening peak traffic flows and the % HGVs, if available. However, I have also gone back to old traffic reports and included the historic traffic counts at each location from 1999-2013. Therefore you can not only see the 2014 figure, but how it compares to historic figures for the previous 15 years.

Depending on your version, when you open it in Google Earth and zoom in you’ll see something like this, where each balloon represents the location of one automated traffic counter:

Screen Shot 2015-12-16 at 20.46.23

Each balloon is labelled with “at a glance” info – the road number and the 2014 AADT traffic level, in thousands. If you click on the balloon, however, you see the more detailed information:

Screen Shot 2015-12-16 at 21.25.13

 

 

So the top bit gives the details of the counter. Each counter can record two separate “channels” of traffic data, which are added together to get the AADT. These are almost always wired up to be one channel for each direction, so the AADT figure is the total for the road. However, in a few cases (e.g. on the M2 foreshore and Westlink) only one channel is used, or it’s used to record two bits of information in the same direction, and in these cases this is clearly indicated. After this is the 2014 data, lifted straight from the 2014 report. At the bottom is historic data.

If a particular figure is missing it will be either because the automated counter did not exist then, because it’s not capable of recording that specific piece of data, or because it was not operating properly at that time. In some cases, counters have been removed due to road upgrades so you’ll see data for a number of years, but then nothing more recent.

You will also note that some very minor roads (like here) have automated counters. Why? This is because TransportNI are keen to estimate how much traffic uses the thousands of miles of low-traffic rural roads we have – these counters are positioned at random around the province to try to get a representative sample that can be used to estimate the usage of the unclassified rural road network.

Link to the KML file which should open in Google Earth.

Enjoy!

UPDATE 21 DEC 2015

My KML file contains all the data for each traffic counter as a single piece of text that you can click. Since I wrote this blog, Bob Harper over at NICVA has worked wonders and further refined the data, separating out the data for each year, etc, as a separate field. The data is now available on the NICVA web site in various formats (CSV, Geojson, KML) which can be used with GIS software. Thank you!

Advertisements

Responses

  1. Great bit of work


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Categories

%d bloggers like this: