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MOTORCYCLE ACCIDENTS AND CASUALTIES IN SCOTLAND 1992 - 2002

CHAPTER SIX: DETAILED ANALYSIS OF FATAL AND SERIOUS ACCIDENTS

6.1 In order to provide a clearer understanding of the nature of motorcycle accidents in Scotland, a detailed analysis of the 180 fatal and serious accidents identified in the cluster analysis was carried out. One accident in the cluster sample was subsequently found to have been a duplicate record and was therefore removed from the database. Table 6.1 shows the composition of the sample.

Table .1 - Cluster sample composition

6.2 It should be noted that the sample is biased towards built-up roads and in this respect it does not reflect the pattern of accidents nationally where most fatal and serious motorcycle accidents occur on non built-up roads. However, the aim on the detailed accident analyses is to provide a deeper insight into the nature of motorcycle accidents in Scotland than can be achieved with the basic STATS19 data alone.

DATA SOURCES

6.3 In Great Britain, the standard STATS 19 accident reporting system contains a great deal of information regarding the attendant circumstances, vehicles and casualties involved in an accident but does not provide a detailed picture of what went wrong and why. Police investigations of fatal and, to a lesser extent, serious road accidents will normally gather more information than that needed to complete the STATS19 form alone. The detailed analysis in this study aimed to utilise this additional information to gain a greater insight into the nature of motorcycle accidents in Scotland.

6.4 Police forces were requested to provide further details on the 179 accidents identified in the cluster analysis. As a minimum, forces were asked to provide a plain language description of the accident, precipitating and contributory factors and details of the motorcycle make, model and engine capacity. In addition, forces were asked to provide supplementary information such as witness statements, sketch plans and photographs although it was appreciated by the project team that this may not be possible within the tight timescale available. With the timescale in mind, forces were asked to submit the information in electronic format wherever possible to minimise delays in data input.

6.5 Data on all 179 accidents was received although the availability of data varied from force to force. Plain language descriptions and motorcycle details were available for the majority of the accidents.

DATA CODING

Motorcycle categorisation

6.6 A coding structure was devised to categorise the motorcycles into broad groups to try to reflect the different appeal of different motorcycles. The categorisation was loosely based on motorcycle categories identified from the website of 'Motorcycle News' ( www.mcn.co.uk). In order to clearly identify the motorcycles from the descriptions in the police data, an extensive database of motorcycle makes and models at the website www.bikez.com was consulted. The categorisation is in no way definitive but the aim was to give an insight into the types of motorcycles involved in different accidents beyond the simple measure of engine capacity. The categorisations are listed in Table 6.2.

Table .2 - Motorcycle categories

Precipitating and contributory factors

6.7 The Precipitating and Contributory Factors system was devised and tested at TRL in 1996 (Broughton et al, 1998). It is designed to be used by the police to easily code the causes of accidents. It should be noted that the collection of precipitating and contributory factors is currently not a requirement of the STATS19 system.

6.8 The Precipitating Factor (PF) is the key action or failure that led directly to the actual impact, so it answers the question 'What went wrong?'. One PF is recorded for each accident: if the factor had not been present then the accident would very probably not have occurred.

6.9 The Contributory Factors (CFs) are the causes of the PF ('Why did this failure of manoeuvre occur?'). At most, 4 CFs are entered in order of decreasing significance.

6.10 In most of the accidents in the current study, police coded PFs and CFs were not supplied and therefore, the project team assessed the available information and assigned Factors to each accident.

6.11 The PF normally presented few difficulties - the plain language description, along with standard STATS19 information such as vehicle manoeuvres and impact details usually provided enough information to assign a PF. However, in two cases, where there was no plain language description, it proved impossible to assign a PF.

6.12 The identification of CFs was much more problematic and was only attempted where information clearly stated the attending officer's view that a specific factor had contributed to the accident.

6.13 Since the PF identifies the failure or manoeuvre which led directly to the accident, the data implicitly show who was judged to be principally responsible for the accident. As a result of this system, the structure of the data allows separate analyses to be made of:

The behaviour of the motorcyclist which led to accidents and;

The behaviour of other road users which led to accidents in which motorcyclists were involved.

6.14 However, it should be noted that in some cases, whilst the project team was able to assign a PF, it was not always possible to determine which vehicle driver was principally responsible. An example is a case on a built-up road in Renfrewshire where the plain text description reads:

'Both rider of bike and driver of car failed to observe lane markings on roundabout, car clipped bike causing rider to lose control.'

6.15 In this case, the PF was assigned as 'failure to avoid vehicle or object in carriageway.' But it is not clear whether the car driver failed to avoid the motorcyclist or vice versa.

6.16 To allow for these situations where it was not clear which vehicle to assign the PF to, an additional field was added to the database called 'Rider Fault'. If a motorcycle rider was judged to be principally at fault (i.e. the PF was assigned to the motorcycle), this was coded 'yes', if the driver of another vehicle was judged to be principally at fault, this was coded 'no' and if it was not possible to judge which driver was principally at fault, the field was coded 'unknown'.

INDIVIDUAL CLUSTER ANALYSES

6.17 Each of the 20 built-up and 20 non built-up clusters was examined individually to try and find patterns in terms of accident types, motorcycle categories, rider ages and whether the rider was at fault. A table for each cluster was produced which enabled patterns in the precipitating factors, motorcycle size and category and rider age to be identified. This process gave pointers to the research team to focus on areas of interest for further analysis.

6.18 Table A4.1 and Table A4.2 (in Annex 4) contain a summary of the main features for some of the clusters on built-up and non built-up roads respectively.

6.19 The analysis found some distinct differences between the accidents on built-up and those on non built-up roads which are summarised below:

Built-up roads

• Tended to be fault of motorist rather than motorcyclist
• A significant number of cars turning right in front of the motorcyclist
• A significant number of 'loss of control' accidents
• A significant number of cars 'u-turning' in front of a motorcyclist
• Mainly lower engine capacity (i.e. less than 500cc)
• Typically roads with 30mph speed limit

Non built-up roads

• Most were fault of motorcyclist
• Most were 'loss of control'
• Over two-thirds involved 'sports' bikes, mostly larger engined (i.e. over 500cc)
• Very few mopeds and scooters
• Typically single carriageways with 60mph (national) speed limits

Day of week

6.20 It can be clearly seen from Table 6.4 that nearly half (46.4%) of the accidents on non built-up roads occurred at the weekend. Most of the accidents on built-up roads occurred during the week with Tuesdays accounting for nearly one quarter of all the accidents on built-up roads within the sample.

Table .4 - Sample accidents by day of week

Precipitating Factors

6.21 It was not possible to assign a precipitating factor in two accidents due to a lack of information. In six accidents, it was possible to assign a PF but it was not possible to determine which vehicle was at fault.

Table .5 - Numbers of precipitating factors by no. of vehicles involved

6.22 Table 6.5 clearly shows that 'loss of control' is the most frequent PF in the sample and accounts for 73% of all of the single vehicle accidents. This is not surprising given that motorcycles require more skill and concentration and have much less stability and grip than cars. The other significant PF in single vehicle accidents was 'pedestrian entered carriageway without care' accounting for 11% of single vehicle accidents.

6.23 'Poor turn or other manoeuvre' was the most common PF in accidents involving two or more vehicles followed by 'failed to avoid object or vehicle in carriageway' and 'failed to give way'.

Table .6 - Frequency of precipitating factors by road type and rider fault.

6.24 It can be seen from Table 6.6 that 'loss of control' was the most common PF in accidents where the rider was deemed to be at fault on both built-up (50%) and non built-up (60%) roads. This was followed by failure to avoid a vehicle or object in the carriageway and poor overtaking (on built-up roads).

6.25 Table 6.6 also shows that poor turn/manoeuvre and failed to give way accounted for approximately 80% of accidents on built-up roads and over 60% of accidents on non built-up roads where the rider was not at fault.

Engine Capacity

6.26 The engine capacity of motorcycles varied between built-up and non built-up roads with smaller engined motorcycles (less than 500cc) being more common in built-up areas. Figure 6.1 and Figure 6. show the distributions of motorcycle engine capacity in the sample for built-up roads and non built-up roads respectively. The peaks in the 501-750cc range in both built-up and non built-up roads probably reflect the increased popularity of these bikes in recent years.

Figure 6.1 - Engine capacity of motorcycles involved in accidents on built-up roads

Figure 6.2 - Engine capacity of motorcycles involved in accidents on non built-up roads

Motorcyclist manoeuvre

Table 6.7 -Precipitating factor by motorcyclist manoeuvre

NB - as some accidents involved more than one motorcyclist, the number of motorcycle manoeuvres is greater than the number of accidents.

6.27 Table 6.7 shows the manoeuvres being performed by motorcyclists immediately before the accident occurred. It can be seen that most were 'going ahead other' (63% of manoeuvres) with significant proportions going ahead on left hand (10%) and right hand (10%) bends. Most of the bend accidents involved the rider losing control (79% for left hand bends and 63% for right hand bends). The other significant motorcyclist manoeuvre was overtaking (9%) with most of these involving the motorcyclist overtaking moving vehicles on the offside. It is worth noting that very few of the motorcyclists were performing turns before the accidents.

Rider Age and Motorcyle Type

6.28 Table 6.8 shows the numbers of motorcyclists in each age group by the motorcycle category separately for built-up and non built-up roads. Sports motorcycles were most common on both built-up and non built-up roads accounting for nearly 50% of the motorcycle types which were known. Sports motorcycles were particularly common amongst riders in their 30s although the whole sample is biased around riders in this age group. Mopeds and scooters were much more evident on built-up roads and mostly ridden by the under-21 year olds.

Table 6.8 - Motorcycle type and rider age

Loss of control accidents

6.29 As shown in Table 6.5, loss of control was the PF in 61 accidents (22 on built-up roads, 39 on non built-up roads) involving 66 motorcyclists (one accident involved five motorcyclists). In one accident, the PF was not assigned to a vehicle and it was not possible to deduce which vehicle was at fault. Of the remaining 60 accidents, 58 were cases where the motorcyclist lost control.

6.30 Table 6.9 shows the frequency of the different motorcycle categories involved in loss of control accidents where the motorcyclist was at fault. Mopeds and scooters account for 24% of these accidents on built-up roads and sports motorcycles account for 68% of these accidents on non built-up roads. It is significant to note that nearly 30% of loss of control accidents on built-up roads involve sports motorcycles. This perhaps reflects the increased popularity of these types of motorcycles, even for commuting use.

Table 6.9 - Frequency of motorcycle categories in 'loss of control' accidents where rider at fault

Contributory Factors

6.31 Although CFs were not available for most of the accidents in the sample, it is interesting to look at the CFs provided for accidents where 'loss of control' was the PF (see Table 6.10).

Table 6.10 - Contributory Factors in 'Loss of control' accidents

6.32 'Excessive speed' was most commonly listed as a contributory factor in 'loss of control' accidents, followed by 'slippery road', 'bend', and 'inexperience of vehicle'.

Road surface conditions

6.33 Motorcyclists are often concerned that diesel spills, particularly on bends or at roundabouts, can create a very slippery surface which can catch out even experienced riders. As stated above, 'slippery road' was listed as a contributory factor in just four 'loss of control' accidents: one where the road was described as just 'wet'; one where the surface was described as 'wet and greasy'; one where there was 'thick ice' and; one where there was 'oil contamination'. Overall, 20% of loss of control accidents occurred on wet or damp roads compared to 25% of all accident types. This will partly be due to lower exposure in wet conditions - motorcycle accidents peak in the drier summer months but it may also be due to riders adjusting their behaviour in wet conditions and riding with more care.

Examples of 'loss of control' accidents

6.34 The following examples illustrate the main types of loss of control accidents found in the study.

Case 1

A male motorcyclist, in the 31-40 age group, riding a 600cc motorcycle going ahead applied front brakes which locked causing rider to lose control. The rider was thrown from the motorcycle and collided with a tree and a wall causing serious injury. The accident occurred on a weekday at lunchtime in spring and the weather conditions were described as fine and dry.

Case 2

A female motorcyclist, in the 21-30 age group, riding a 600cc sports motorcycle, strayed onto the opposite carriageway on a sweeping left hand bend, managed to correct and then lost control, crossed onto the opposite carriageway and collided with an oncoming car. The rider was thrown from the motorcycle and landed on the road causing serious injury. The car left the road and collided with a roadside sign resulting in a slight injury to the driver. The accident occurred on a weekend afternoon in late spring. Weather conditions were described as fine and dry.

Case 3

A group of male motorcyclists, all riding large engined sports motorcycles, travelling on a leisure run collided with each other after the lead motorcyclist, in the 31-40 age group, lost control on a right hand bend. The motorcyclist immediately following the leader suffered fatal injuries when his motorcycle landed on top of him. Two of the other motorcyclists suffered serious injuries and a fourth suffered slight injuries. The accident occurred on a weekday afternoon in early autumn. The weather conditions were fine and dry.

Case 4

A male motorcyclist, in the 21-30 age group, riding a 750cc sports motorcycle, approached a sharp left hand bend apparently at excessive speed, locked the rear wheel, lost control and mounted the kerb causing the rider to fall from the motorcycle. The rider suffered fatal injuries as a result. The accident happened on a weekend afternoon in summer. Weather conditions were fine and dry.

Loss of control accidents - summary

• Loss of control was the most common cause of motorcycle accidents, especially those on non built-up roads.
• Over 40% of loss of control accidents occurred on bends suggesting that riders over estimate their cornering abilities.
• There is some suggestion that excessive speed was the predominant contributory factor in loss of control accidents.
• There is some suggestion that road surface condition may be less of a factor than rider error in loss of control accidents.

'Non rider fault' accidents

6.35 As previously stated, most of the 'rider not at fault' accidents were caused by drivers of other vehicles turning in the path of or failing to give way to the motorcyclist. These accidents can be considered together as they generally involve a lack of awareness on the part of the other vehicle driver.

6.36 It should be borne in mind that in many of these accidents, the behaviour of the motorcyclist may have contributed in some degree to the accident. A common example is where the motorcyclist overtakes a line of vehicles which are waiting behind a car waiting to turn right into a side road. The driver of the car makes the manoeuvre and collides with the overtaking motorcycle. It could be argued that better forward anticipation and observation on the part of the motorcyclists may have allowed him to avoid the collision. However, the accident was precipitated by the car driver turning right without being aware of the motorcyclist.

6.37 Most of these accidents occurred on built-up roads and they can be split into 3 main categories:

• Driver turns right from main road into side road
• Driver emerges from minor road onto main road (and turns or fails to give way)
• Driver performs u-turn in front of motorcycle (sometimes in heavy traffic)

6.38 As stated above, the common thread in these accidents is the driver's lack of awareness of the presence of the motorcyclist. With this in mind, the characteristics of the drivers involved were examined. For simplicity, 2-vehicle accidents were examined.

Driver age

Table 6.11 shows the age distribution of drivers in 'non rider fault' 2-vehicle accidents. Over 30% of these accident types involved drivers in the 31-40 age group.

Table 6.11 - Ages of drivers in 'non rider fault' 2-vehicle accidents

Driver Sex

6.39 Table 6.12 shows the sex of drivers in 'non rider fault' 2-vehicle accidents. Males make up over three-quarters of the drivers which is similar to the make-up of the whole sample. There is no evidence that either sex is more prevalent in these types of accidents.

Table 6.12 - Sex of drivers in 'non rider fault' 2-vehicle accidents

Lighting conditions

6.40 The lack of driver awareness may be reflected in the numbers of accidents occurring at night. Table 6.13 shows that over 40% of 'poor turn/manoeuvre' type accidents occurred in darkness. This is higher than may be expected.

Table 6.13 - Lighting conditions in 'non rider fault' 2-vehicle accidents

Contributory Factors

6.41 Although CFs were not available for the majority of accidents in the sample, it is interesting to look at the CFs for 'non rider fault' 2-vehicle accidents (see Table 6.14). It can be clearly seen that in 'poor turn/manoeuvre' and 'failed to give way' accident types 'Did not see' is the most common CF given, followed by 'Inattention'. It is interesting to note that 'excessive speed' is also listed in three accidents and these all relate to the behaviour of the motorcyclist.

Table 6.14 - Contributory factors in 'non rider fault' 2-vehicle accidents.

Pedestrian Accidents

6.42 There was a small number of accidents involving pedestrians (eight accidents). All but one occurred on built-up roads and the majority were 'blamed' on the pedestrian crossing without due care (75%). The issue here may be that pedestrians, like drivers, fail to see motorcyclists or are generally not expecting them to be around.

Examples of 'non rider fault' accidents

6.43 The following examples illustrate the main types of 'non rider fault' accidents found in the study.

Case 1

A male car driver, in the 31-40 age group, travelling along an urban road (30mph) turned right from the main road, without signalling, into the path of an oncoming motorcyclist (a male in the 41-50 age group riding a large engined traditional motorcycle received serious injuries). The accident occurred on a weekday evening in winter in the dark. The weather was fine but the road surface was described as 'wet or damp'.

Case 2

A male car driver in the 61-70 age group, was stationary on an urban main road (30mph) intending to 'u-turn', downstream of a traffic signal junction. A male motorcyclist, in the 21-30 age group, riding a large engined traditional motorcycle was waiting to go ahead at the traffic signals and as the lights changed to green he accelerated ahead. The car driver began his manoeuvre and collided with the motorcycle, the rider received serious injuries. The accident occurred on a weekday morning during rush hour in late winter. The weather was fine and the road surface was dry.

Case 3

A male van driver, in the 31-40 age group, failed to give way at an urban crossroads and ran into a male motorcyclist, in the 41-50 age group who received serious injuries (riding a large engined traditional motorcycle). The accident occurred on a weekday afternoon in summer. The weather was fine and the road surface described as dry.

Case4

A male motorcyclist, in the 31-40 age group, riding a large engined sports motorcycle, was travelling along a busy urban thoroughfare when 2 female pedestrians stepped into the path of the motorcycle at a pedestrian crossing after looking the wrong way. The motorcyclist braked sharply and the rider fell from the motorcycle receiving serious injuries. The pedestrians were not injured. The accident occurred on a weekend night (dark) in summer.

'Non rider fault' accidents - Summary

• More common on built-up roads.
• Usually involve another driver failing to give way, turning or 'u-turning' in path of motorcycle.
• 'Did not see' and 'inattention' most common contributory factors.
• Higher than expected number occurred in darkness.

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