How is road accident data collected?
Why can't I see full details of individual road accidents?
What is a road accident?
Why do you refer to 'road accidents' when other authorities refer to 'road collisions' or 'road crashes'?
What is a road accident casualty?
What is a slight/serious/fatal casualty?
What is a slight/serious/fatal accident?
How often is the data updated?
How accurate is the information?
Why 'reported' road accidents?
How is the traffic flow data calculated?
Road accident data is collected by the Greater Manchester Police. This website only contains information about road traffic accidents that involved personal injury and took place on the public highway. Deaths or injuries occurring on the public highway without a vehicle being involved are not classed as road traffic accidents. Accidents that do not become known to the police, or only become known 30 days or longer after their occurrence are also excluded. Accidents are recorded by the police using the Stats 19 form. This is a nationally agreed form for the collection of accident data and a PDF copy can be downloaded from the Department for Transport website.
The number of injury accidents not known to the Greater Manchester Police is not easily identified. It would seem reasonable to assume that all 'fatal' accidents are reported, but these represent only a small proportion of the total. However, the limited evidence available indicates that 'serious' and 'slight' accidents are under reported. It has been assumed historically that 20% and 35% respectively have not been reported.
There are two reasons why not all the data available to TfGM can be displayed on this web based interrogation system. Firstly, the computing power and programming required to display all the information would be considerable. In this first release of the web based Greater Manchester Road Accident database, the number of fields have been kept to the ones that we thought would be most useful. We would welcome your feedback on other fields that you might find useful, and if practical they will be considered for future versions of this system.
Secondly, to publish certain fields may lead to the individuals involved being identified. Such data could contravene the Data Protection Act and is considered exempt under the Freedom of Information Act.
If you are a member of the public and you wish to obtain more details of accidents please contact your local authority.
A road accident is the incident itself. Examples of road accidents include:
Many road safety professionals refer to 'collisions' or 'crashes' rather than road accidents since they believe that all such incidents are preventable and therefore cannot be an ‘accident’. This view is not universally accepted, and there are problems with the alternative terminologies since many people would regard a collision or crash as being between two vehicles and not between a vehicle and a pedestrian. There are also 'accidents' where no 'collision' occurs, for instance where a bus brakes hard to avoid another vehicle, and a passenger on the bus falls and is injured.
In Greater Manchester, different councils have different viewpoints on which terminology should be used. However, it has been decided that at a Greater Manchester level, the term road accident should be used. This is the term that most members of the public would use and is also the one used by the Department for Transport on the national form used for the collection of the data (see above).
A fatal casualty is someone who dies as a result of the accident within 30 days. A serious casualty is someone who receives a serious injury as a result of the road accident. Examples of a serious injury are:
A slight casualty is someone who receives a slight injury as a result of the road accident. Examples of a slight injury are:
Anyone who is merely shaken and has no other injury is not considered to be a casualty unless they receive or appear to need medical treatment.
A fatal accident is any accident where one or more people received a fatal injury as a result of that accident.
A serious accident is any accident where one or more people received a serious injury as a result of that accident and no-one received a fatal injury.
A slight accident is any accident where one or more people received a slight injury as a result of that accident and no-one received a fatal or serious injury.
The data on the web-based version of the database will be uploaded in three-monthly blocks. It is expected that the data will be available as follows:
We currently have data for 1st January 2006 to 31st March 2015. The next update is due in September 2015.
The STATS19 data is what has been recorded by the police at the time, or immediately following an accident. Some of this reporting will have been over the counter by members of the public and will represent their personal views of what happened rather than what may have actually happened.
As such, the data can be used to find out information about the types of accident that may be occurring at a particular location, or trends in accidents and casualties. It should not be used to look at an individual accident to find out what happened.
For more information on how accidents and casualties are coded, full details can be found on the Department for Transport website (PDF format).
Very few, if any, fatal accidents do not become known to the police. However, it has long been known that a considerable proportion of non-fatal injury accidents are not reported. The Department for Transport have changed the titles of all of their publications to more closely reflect this, and we have decided to do the same locally. We therefore now refer to ‘reported’ accidents or casualties to make clear that there may be other road accidents and casualties that are not know to us.
Traffic flows are collected in two ways:
1. Manual Roadside Observation
The traffic flows passing a point on the length of road are counted by teams of skilled and experienced traffic surveyors who observe and record the traffic from safe locations adjacent to the highway. The period counted is generally from 07:00 to 19:00 hours.
2. Automatic Traffic Counting
The traffic flows passing a point in a length of road are counted by automatic electronic traffic data loggers. In most cases vehicles are sensed by magnetic induction as they pass over loops embedded in the road surface and the information is recorded by the loggers. This data is collected 24 hours a day, every day, year round and GMTU has a large number of sites at various locations around the Greater Manchester area.
These data are returned to the GMTU office for data validation and are then added to our databases of traffic flow information.
What is shown on this website?
The data presented on this website utilises both these types of data to give two flow figures for each length of road:
AADT Annual Average Daily Traffic Flow
AAWT Annual Average Weekday Traffic Flow
NB. Unless otherwise stated these flows are two-way totals and are therefore all traffic passing the point counted. For two-way flows the direction is given as Both, for one-way flows the direction of the flow is given N,S,W,E etc.
Also given is a TfGM Forecasting and Analytical Services reference number for the count site location.
Definitions of traffic flow figures
AADT - Annual Average Daily Traffic Flow:
This is an estimate of how much traffic passes the count point on average each day Monday to Sunday.
AAWT - Annual Average Weekday Traffic Flow:
This is an estimate of how much traffic passes the count point on average each weekday Monday to Friday.
How are these traffic flow figures calculated?
Each count site is generally counted by manual observation for twelve hours between 07:00 and 19:00 hours. This flow information is then factored to produce the two annual average traffic figures quoted using the data collected from the automatic traffic counting sites which operate all day, every day, and year round.
More detailed information on how these flows are calculated can be found on the main TfGM Forecasting and Analytical Services website in Report 1387.
NB. The Department for Transport (DfT) also gives factored count figures, sometimes for these same sites. These may differ from those presented here as the figures on this website use local Greater Manchester factors rather than national ones. The DfT website can be viewed at: www.dft-matrix.net.