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Case Studies, Project Updates, Industry Insights and Think Pieces from the Transafe Network team

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Quantitative Risk Assessment: Air vs Land

Updated: Jun 4, 2020

It's often the case that we hear the mantra that it's safer to fly than to travel by road. Often, clients will have spent large sums of money on choosing air travel over road travel on safety grounds. But are these benefits real, or imagined?

In short... it depends. And you'll never know unless you conduct a Quantitative Risk Assessment (QRA). So what does a QRA consist of, and what kind of results may it bring? We were commissioned to conduct a QRA for a company that needed to move people from Amman in Jordan out to a base serving an operations site near the border with Iraq. All options included a 20km blacktop and 46km graded road section to get from the base to the operations site.

Their options were:

  1. Drive 340km to base near operational site

  2. Fly 216km to an existing airfield (which could already accept smaller aircraft but would require an upgrade costing several million USD to be able to receive larger aircraft) and then drive 75km to the base

  3. Fly 287km to a new purpose-built airstrip at the base (with significant difficulties in gaining permissions for the construction so close to the border and an even bigger cost of complete construction than the upgrade option)

The three options are shown in the diagram below.

The Transafe Network team sought out local data to combine with existing international data sets on aviation safety for the aircraft types and operating conditions to be encountered. These included

  • Jordan Specific Aviation Safety Data

  • Jordan Specific Road Safety Data for the speficific routes involved

  • Jordan Specific Bus Safety Data

The team then assessed what could be technically available in the local aviation market and within what timescale. The team then used Regional and International data to adapt the risk quantification model, and modelled in the logistics forecast personnel movements, a previously conducted Aviation Feasibility Study, and guidance from the relevant industry bodies.

The team calculated the risk values for two options of aircraft for the flight sections (large and small, available locally) with transport by road by either minibus (for the small aircraft) or coach (for the large aircraft). They also calculated the risk values of travelling by coach or light vehicle to travel the entire route by road. This included examination of the coaches available from local suppliers - one supplier had a one year old Mercedes coach, a five year old MAN coach and a number of TEMSA coaches. Our client was initially drawn to the Mercedes as being one of the newest on the fleet and a trusted brand. However, examination of the vehicles found that the MAN was a fully UNECE R66, R17, R80, R14 & R36 compliant vehicle, and the TEMSA coaches were all made to EU specificatons, the Mercedes badged vehicle was actually just a Mercedes built rolling chassis from their factory in Egypt, the body for which had been locally coach built in Jordan with zero compliance to international standards in roof strength for rollover, window glass etc. and would have been a significantly higher risk vehicle to utilise.

All of this number crunching created a value of Implied Fatalities Per Million Passenger Kilometre, which then translated into a figure of implied Fatalities Per Year of anticipated operation. The final results are shown in the diagram below:

Presenting the information visually like this (with the actual models of aircraft available being used in the graphic) clearly showed the client's management team that whilst the safest option would be constructing the new airstrip for the larger plane (DHC-8, ATR 42 or equivalent, at vast expense and no certainty of getting permission), the second safest option would be the larger plane at the existing airstrip (Beechcraft King Air or equivalent, again requiring several million USD in upgrades), but that this was on a par with the option of travelling by coach all the way.

The cost of each option was reflected in the diagram below, which mapped Cost against Ease of Implementation, with the risk colour coded:

The coach option clearly represented a very significant cost saving, which would enable the client to invest in safe vehicles, effective driver training and management, double crewed coaches and road safety engineering and community initiatives along the route, improving safety for the whole community and saving money whilst achieving a good level of safety. It was initially decided by the client that everyone except VIP's would therefore travel by coach to the base, with VIP's still travelling in light vehicles - however, when the VIP's in question were shown that they would be taking on over 7.5 times the risk of fatality by doing so, they wisely decreed that all personnel, however important, would be taking the coach. The long term aim of pursuing construction of a better airstrip will continue, but until then, the project was able to proceed knowing it was being as safe as possible.

If you're interested in finding out more about conducting Quantitative Risk Assessments, contact:


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