What's the problem? Recording and investigating
Welcome to the Road Accident Indepth Study (RAIDS) team at the UK's transport research agency TRL (pictured above). This team of engineers attends and investigates serious crashes in the UK to capture and analyse data on the consequences and causes. They database the evidence they find, which can subsequently help inform appropriate road safety interventions to stop future crashes.
If only all collisions, the world over, were attended by teams like these. We would know so much. Road safety management starts with understanding the problem. Yet different countries have different, and often inadequate, systems for even recording basic information about fatal and serious injury crashes; the when and the where, involving what vehicles and people, and the level of injuries. In the UK, the RAIDS team is only funded to attend a proportion of serious crashes.
Conflicting information and under-recording
Sometimes information is recorded by different agencies with conflicting results. For example, numbers of casualties collated by police might not match numbers of casualties collated by hospitals. Ways of recording injuries may differ. For example, a death may not be recorded as a death if it happens a certain number of days after a crash. Or a life-changing, and very serious injury such as loss of a limb may not be recorded as very serious because it hasn't been life-threatening.
There is widespread belief that numbers of deaths and life-changing injuries are consequently under-reported, grossly so in some countries. Even in the richest nations, this is so. New Zealand estimates that, while deaths are all recorded, only two thirds of injuries on its roads are recorded. 
There are simple systems that can be implemented to assist basic data collation. For example, the World Bank has worked in the Philippines (a country plagued with deaths of motorcyclists and pedestrians) to enable local agencies to start recording crash information on a computer rather than on paper, enabling the government to see clusters of crashes and other trends and take action. The DRIVER project (Data for Road Incident Visualisation, Evaulation and Reporting) uses cheap, open source software.
The Philippines and the World Bank has also worked with the Southeast Asia ride-hailing service Grab to obtain a stream of GPS data from Grab vehicles that can provide traffic statistics, including speed and flow of traffic.
Holly Krambeck, World Bank Senior Transportation Specialist, says: “Through this initiative, the Philippines will leapfrog traditional approaches to road safety, traffic management, and planning. The country is among the pioneers in the region.”
Data transparency and targets
As well as recording data about crashes that kill and injure people, it's important that this information is made freely available to everyone - people living in those countries, and between countries for comparison purposes.
There are increasing efforts to harmonise collision data recording methodologies so data can be compared between countries accurately. The International Traffic Safety Data and Analysis Group (IRTAD) aims to raise standards of collision data and collects and shares similarly-collected data from 40 countries and publishes open access annual reports about levels of fatalities and road safety interventions in these countries.
Countries need to be held accountable for their levels of deaths and injuries on roads, and set targets and plans for reductions.
The question "why did a crash happen?" is much harder to answer. Understanding why a crash happened often requires detailed investigation, carried out by qualified professionals, including engineers and other specialists who can study vehicles, victims, drivers and the road environment.
In the poorest nations, there may be no or little investigation. Even in the richest nations, investigation is often too limited. Its extent may be dependent on outcome, with crashes resulting in death resulting in more investigation than crashes resulting in injury.
The motivation for investigation is also a factor. If there is a chance a criminal prosecution may be brought, then police or agencies contracted by the police may investigate. In some countries, it is possible to bring a civil law case, and investigation may therefore be carried out on behalf of the victim or their family in order to prove a case for compensation. Sometimes, academic institutes, in partnership with police, are funded, usually by government agencies, to do indepth, on the scene, studies of crashes resulting in deaths or serious injuries. A great example of this is RAIDS in the UK, but there are others too. These studies provide a wealth of data useful for guiding road safety interventions. However, these data sets may be frustratingly small, or have little longitudinal strength due to funding often being intermittent for such projects.
Calls for collision investigation agencies
Countries should have a collision investigation agency, responsible for conducting indepth studies of crashes resulting in deaths or serious injuries. In Britain, for example, there are agencies tasked with investigating rail, aviation and maritime disasters, but no similar agency for road crash investigation. British NGOs including Brake and PACTS are calling for the establisment of such an agency.
Richard Cuerden, chief scientist at the UK transport research agency TRL, says: “Preventing road deaths and injuries requires independent evidence to inform cost-effective policies and to evaluate and improve interventions over time. The information necessary to develop achievable casualty reduction strategies includes national road collision reporting to measure the size and nature of the problem and specialist in-depth investigations, which, with a representative sample, provides an understanding of the causes of collisions and the resulting injuries. Without good information, the Safe System approach cannot be effectively followed.”
Further reading / learning opportunities:
From the UK: PACTS Collision Investigation: how can we learn more? conference minutes
 2016, OECD/ITF Annual report on road safety, p380
 2016, World Bank press release, Philippines: Real-Time Data Can Improve Traffic Management in Major Cities