The Use of Mountain Bikes for Search and Rescue
On Friday I posted a news item on the First National Search and Rescue Mountain Bike Instructor Scheme being run by Black Badge. This sparked a debate; on whether it actually was the first but also on the use of mountain bikes for lowland search and rescue. A number of ALSAR Units now run mountain bike teams and all have reported favourably on their use.
Back in 2006, however, when a couple of teams first postulated their use I was asked to look into it. The following is my response;
Following the request to investigate any research into the use of mountain bikes for SAR I undertook both internet searches and posted requests for information on SAR forums and discussion groups. Although several suggested contacts were given I found no evidence of any serious research into their use.
Robert Koester, who has carried out sweep width experiments in the US, responded stating;
“I’m not aware of any sweep width studies done yet for mountain bikes.
…I would expect the results to be similar to what we found with mounted
searchers. Ground searchers had a larger (better detection index) sweep
width off-trail in challenging terrain than the mounted searchers who had to
contend with directing the horses. On the open road the mounted searchers
had a larger sweep width due to a height advantage and little to no need to
concentrate on the “next step”.”
In the absence of empirical data, therefore, I tried to do the mathematics of using a mountain bike team for searching a route and path compared to a three searcher foot team – comparing different variations of speed and sweep width to see whether in the first instance it was appropriate to use mountain bikes for search and whether their use would change with the search environment.
Before I present the conclusions however, I must state that although I am confident of the results it would be best to conduct proper sweep width experiments to assess both the appropriate speed for bike search teams and sweep width estimates.
The aim of all searches is to maximise the Probability of Success (POS) of the search. POS is a product of the Probability of Area (POA) and the Probability of Detection (POD). Therefore, comparing two search resources searching the same area it is the POD that is the relevant factor.
The POD of a search resource in an area is a factor of the size of the area against the search effort put into it. This is described by the Coverage of the search resource, which is the distance travelled by the search resource times by the sweep width.
The example of a three searcher ALSAR foot team covering a 1km route and path is as follows:
Area to be searched: 2m wide track plus 5 m either side gives a 12m wide track by 1000m length equals 12 000m2 total length.
Distance travelled by searchers: Assuming a straight line and no purposeful wandering, 1000m by each searcher, 3000m in total.
Sweep Width: Taking a rough average sweep width figure of 54m (the 2004 experiment results ranged from 16m to 142m)
Therefore the search team’s “Area effectively swept” was 3000 x 54 which equals 162 000m2. This gives a Coverage of 13.5
Using Koopman’s exponential detection function we can translate this to a POD of 99.99%
Doing the mathematics of the bike team is slightly more complicated. According to the advice given the first bike in the team is purely there for navigation – to give warning of hazards etc. They, therefore, have a vastly diminished sweep width figure.
The two further bike team members can concentrate more on search but it must be recognised that they still will not have the same detection index that foot searchers will because of the need to concentrate on cycling. For the first calculation I will assume that they have half the sweep width figure i.e. 27m.
Area to be searched: Remains the same at 12 000m2
Area effectively swept: For the first bike 1000m x 2m (it is assumed they would notice a body in the middle of the track!). The two remaining bikes cover 2000m x 27m. This totals 56 000m2.
This gives a Coverage, therefore, of 4.6.
Translating into a POD of 98.9%.
The advantage of the bike team, of course, is that rather than taking approx. 30 minutes to cover the track as an ALSAR foot team would at a searching speed of 2km/h, they would take approx. 12 minutes at 5km/h.
This means that their probable success rate (PSR – an important calculation using the Charnes-Cooper algorithm) is greater than that of a foot search team and, therefore on the basis of these rough calculations, should be used in preference to the foot team if both are available.
There are a number of caveats to that, however.
Without doing the mathematics for each case it can be proved that the bike search team is of far greater benefit used in areas with a higher sweep width figure (i.e. less dense woodland etc.) and where they can travel faster (because of better tracks etc. i.e. less need to concentrate on riding.)
As the search environment becomes thicker, or the team have to slow down more and concentrate upon riding more their effectiveness diminishes. At very low sweep width figures the bike team would have to repeat their search area or a new resource allocated for the search manager to have a reasonable confidence that the misper was not in the area.
Any advice to search coordinators, therefore, should recommend the bike team’s use for easy to ride tracks in less dense woodland or open areas. A foot team would be more suitable for a harder to ride, denser search environment. (Obvious I know, but provable and worth stating)
What needs to be done, however, is to carry out field trials at the very least (preferably sweep width experiments although these require greater manpower than might be available). These would need to ascertain the “best” speed (or at least what the average speed for the bike search team is) and some sort of detection index (again at the very least the AMDR for the bike search team). These would allow much more accurate mathematic investigation and proof.
The trials that Jennie writes about in her comment were part of Wilsar’s response to my last paragraph that at the very least field trials needed to be run to satisfy us that it was a useful efficient search resource.
November 15, 2009
· 
Robert Bradley · 
12 Comments
Tags: ALSAR, Bike Search Team, Charnes-Cooper Algorithm, Lowland Search and Rescue, Mountain Bikes, Mounted SAR, National Search and Rescue Mountain Bike Instructor Scheme, POA, POD, POS, Probabililty of Success, Probability of Area, Probability of Detection, Probable Success Rate, PSR, Robert Koester, Route and Path Search, Search Effort, Search Theory, Sweep Width, Sweep Width Experiments, Track Length, Wilsar · Posted in: Search Research, Search Thoughts
12 Responses
However, all that said, mountain bikes are proving to be a valuable asset to get foot teams quickly to search areas which would otherwise be difficult to park at or access from the road.
Also they have been very useful to use as mobile repeaters throught out a search, passing on messages from teams to control and vice versa, when radio comms is limited by terrain or control’s location.
The maths of all that were very interesting.. Do you think that it would be useful to try to set something up to assess the effectiveness of bike searchers more formally?
In my last post I didn’t mean to suggest that bikes were “proven” to be effective, I just meant that there was some evidence to suggest that they could be.
I am currently setting up a team with bikes at the very heart of what we do. The use of bikes is multi-faceted. They can be used for searches, transporting of equipment, communications, personnel welfare. We are currently looking at purchasing 2 ambulance responder bikes with 4 search bikes. As a team we are really looking to push development of bike use, the bikes themselves, and the equipment they can carry.
We have come up with an interesting stretcher design that converts into a wheeled stretcher by utilising the bikes. We also have some ideas about folding long boards.
In addition to this we are also currently evaluating rider techniques both urban and rural. I am a qualified instructor, and have many years SAR experience both on land, and more recently, water.
Our area currently has a varied set of terrains from hills just under 1000ft to flat flood plains and urban and inner city areas. Bikes have an enormouns part to play.
As part of our evaluations I have been drawing up plans for a tiered SAR bike qualification that builds off the back of the ALSAR structure. I am hoping to have a basic proposal completed shortly.
I would be really interested to hear what people think about our ideas.
Hi Leigh,
Have you spoken with any of the existing ALSAR teams who are already heavily into the use of bikes?
Rob probably has a list of them and most advertise the use of these on their websites.
Also, give the Public Services Cyle guys (Andy Miles is a good start) a shout, they’ve done a lot of work in looking at bikes for SAR use.
For my own part I can see how bikes play a major part in search support but i’ve yet to see much hard evidence of their use in actual searching (see previous blog posts on here)
Is the rider searching or riding? How well can they do both at the same time? What are the parameters for using bikes for search? – At the moment I’m not sure they are good enough to build an entire team around.
Where will ATBRU be operating? Is there an exisitng ALSAR or MRC team for that area and have you spoken with them yet? They’d be able to advise on workload for the area and you’d need to be able to work alongside them.
How about heading over to SARworld (www.SARworld.org/forum) and posting something up on there as well.
Kris,
I’ve not done a full bike search course, but I’ve been on a trial of one, and you search, but you essentially have, from a team of three, a TL who acts as health and safety, etc, and searches when they can, and two searchers who do half a cube each – looking out to one side, front and back. The bike team as a whole completes the searcher cube and provides a hasty search of a route and path.
I beleive some units use bikes to go out and look for track traps, and to search the most significant reflectors quickly. They seem to be a very versatile resource which makes the most of speed not being a factor in detection rates. And also, the team do not have to remain on the bikes the whole time – bikes can be used to access a sector for an area search more quickly than a foot team and sometimes more easily than in a car. The bikes can then be locked up and a foot search can be done if the bikes aren’t appropriate for the area.
Leigh,
The two units I know of that use bikes (and I am sure others do too) are Wiltsire and Sussex search and rescue. They’re your best source of information about the bike side of things. I’m sure other teams who use bikes would also be willing to share their experiences.
I would like to think that Isis will look at bike searching once we’re a full ALSAR member and have some more funds. It’s not a realistic thing for us yet.
————————————————————–
If I’m wrong about anything please set me straight..
Sorry Jenny, but still not convinced on the search aspect of bikes.
Support yes, no problem with that of course. As a transportation method then great.
As for the cube being split across 2 cyclists (looking backwards?) then you are saying that it takes 3 cyclists to do what 1 foot searcher can do, but they can do it faster. And a single bike rider being responsible for the H&S of 2 cyclists means the separation would have to be very small (otherwise its a bit pointless) – So when all is said and done, 1 bike team (of 3) equals 1 foot searcher in terms of broad detection ability? (maths aside for now)
So for clearing a route/path then ok, as long as the misper is on the path or just off it but highly visible then I can see there is merit. But typically mispers can be many meters off a route/path. How useful do bikes become then (or are they not deployed for this scenario?) – Could WIlsar or Sussar perhaps comment on the ‘search ability’ side of things for bikes?
I’m sold on the use of bikes for support and as a transportation aid (and also for searching for the obvious i.e. the misper walking or static actually on a path) It’s different tools for different jobs but what I’m still struggling with is the idea of detection ability from a bike and I’d like to see/hear more evidence on this.
I feel that there is a danger here of something that has been written being misunderstood and taught and re-taught until it becomes a “fact” – a fact with no basis in actual fact!
It happened first with Dementia mispers; they always travel in straight lines! If you ever read the “original” quote it states no such thing; but that hasn’t stopped this “fact” becoming a truth you hear over and over again.
The same seems to be happening with the speed of search.
The speed of search affects the detection rate! Obviously!
You cannot run down the track and hope to see as much if you walked normally…
This misunderstanding seems to have grown from the US Coastguard sweep width experiments results; which reported that the average speed of searchers was “remarkable consistent” at 1.75km/h. It goes on to state that “searcher speed when kept between 1 – 3km/h did not affect sweep width”. It then also goes on to state “it is assumed at much slower or faster speeds a difference would occur.”
I shall just repeat that last bit … “it is assumed at much slower or faster speeds a difference would occur.”
However, all that refers to foot search. We all await test results from bike search … a protocol for which is, hopefully, being written this year!
I will obviously have to research and write more on this subject soon!
Thanks Kris, Jennie and Robert for your comments.
To clarify we are not solely using bikes for search purposes. We will be a traditional search team as well. We are in quite a grey area in Worcestershire because we have a wide variety of search terrains from hills to rivers.
We have started to talk to ALSAR particularly Adrian and Jo, who have been an enormous help! There is currently no land search team on our patch but there are 2 or 3 water teams who try to double up with land search. I am not sure how others feel about disciplines being mixed but I consider this to be a disadvantage as they cannot practise and develop to the same standards as a single discipline team. I am hoping that by working towards approval standards we can become an ALSAR team. We already have the best part of a team qualified well above first aid requirements, and radio trained. They are all CRB checked to, so it is the search element and controller / management element to work on.
Some interesting work going on at the moment and some very useful contacts and partnerships being made. Watch this space!
As goes the bikes … well we are trying to view them with search and mountain bike heads on. We have about 40 years of experience on bikes between us so again … Watch this space.
It is really good to open dialogue with other teams and I am very much looking forward to meeting you all at some point.
Leigh
Bikes are a very effective search resource. You search in a very different way, but you do make finds. There seems to be an implication that if you are not cubing you are not searching. If we look at how many dog walkers discover mispers (and assume that not many of these people are cubing) then we can assume that you can discover mispers without this technique. Bike searching cannot be squeezed into a foot search model (a search dog doesn’t cube, but still finds mispers).
I have not heard the ‘half a cube’ expression before and hope not to hear it again. It is daft.
A bike searcher sees a lot less than half a cube. however, they cover a lot of ground. Effectiveness is reduced, but efficiency is improved. Whether this trade off is acceptable, and whether you deploy bikes, is a decision for a search management team on the ground to make, based on misper type, terrain, and personnel. It cannot be decided on forums. As with the Pope’s view on condoms, I’d say; if you don’t play the game, don’t write the rules!
For searching to progress and evolve, we need to have no ‘sacred cows’ that cannot be challenged. As such; trackers, dogs and bikes use different techniques to foot searchers. An effective and efficient search uses multiple resources in the best way.
If anyone would like to try out the game, contact me and we’ll look to involve you in one of our bike training events.
Hi Johnnie,
I’m not sure where to start on this. I’ll start from the bottom and work up
So, as you quite rightly point out, there are no sacred cows, and as such I am challenging the use of Bikes as a detection resource (not as any other form of resource) – As I’ve always said I am open minded on their use, so prove their worth for detection or at least provide more ‘evidence based’ information on them. I’m happy to come and look at them in action and the training but to be frank I’ve seen people cycling before and I’m not sure that the physical act of watching them search proves that they are a good detection resource.
As for ‘make finds’ well any search resource can make a find. Even a blind man can find a misper if he trips over one.
Of course Dogs don’t cube, but when you have their scenting ability you don’t need to! Bikes cant be squeezed into a foot model but how do bikes compare to foot searchers?
If search managers are going to use bikes as a search resource and to deploy them effectively then there needs to be more infomation than ‘they make finds’ and ‘cant be decided on forums’
Daryl >> Does the handler or the supporter ‘cube’ when searching? (just interested in knowing)
I’d just like to see some objective information on the use of bikes for detection so that I (as a Search Manager) can decide on when/where to deploy bikes for detection. The fact that they are fast isnt good enough.
1. Would other search managers out there deploy bikes as a detection resource?
2. If so, what are the parameters that you use for this?
3. If you specifically dont use bikes for detection, why not?
Do UKLSI include the use of bikes as a detection resource in their SC training? If so, what are the parameters?
How do bikes compare to foot searchers?
They typically search at four times the pace with a considerably lower POD. How much lower depends on the terrain. Whether or not you deploy them depends on a number of factors. If you are looking for a misper type with a large track offset figure then bikes are a less desirable tactic than for a misper who is more likely to remain on or near the path. They are limited as riders to the type of terrain they can search, but the searcher’s ability to dismount increases their flexibility. I believe bikes are good for the quick hits, or ‘low hanging fruit’ in business jargon. Ideally I would search a R&P with bikes, dogs, and foot teams. I favour using very hasty resources (runners and bikes) in the early stages to increase the survival chances of the easier to find mispers. This is partly because Rob has convinced me (through mathmatics, examples and exercises) that speeding up a search has a disproportionately small effect on POD, and partly because of the time=survivability principle.
All of my Search Controllers have done our bike searching course, so rather than looking at bike searchers, they have searched by bike in real conditions and understand the resource and its limitations well. A Search Controller needs to do it to understand it (I did some kayak search training with WilSAR to better understand this resource, even though I hate being in the water)
Bikes suit our terrain, and misper types, in some searches. Sometimes we deploy them, sometimes we don’t. I would not wish to tell any other unit which resources they should have, or when to deploy them, but I do believe it is best practice to try something before discounting it. Go on, give bike searching a try!
Thanks Johnnie,
Has Rob got your contact details? I’ll give you a shout about coming along to see the bikes (or bike training) in action.
Kris
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