A78 Hunterston Roundabout to Highthorne: Survey, Hazards, Risks, Mitigationsmarch 2013

A78 Hunterston Roundabout to Highthorne: Survey, Hazards, Risks, MitigationsMarch 2013

To be read in conjunction withA78 Pictorial Survey, Hunterston Roundabout to Highthorne

This work starts at the south side of the Hunterston Roundabout; the roundabout itself is not included (the detail of the Ordnance Survey map shows an accident cluster in the vicinity of the roundabout).

Unless otherwise stated, distances are measured to or from the near edge of a junction.

Interval Characterisation

The A78 (T) is the main north-south route for North Ayrshire. It is a busy road, but seldom sees significant queuing / congestion. Usage includes private vehicles and all sizes of commercial vehicles. This 2.25km interval of the A78 runs through an agricultural area, and comprises 2 distinct sections. It is a single lane carriageway; the national speed limit applies (60mph for cars down to 40mph for heavy trucks).

The northern 1km from the Hunterston Roundabout to just south of the Kilruskin junction was realigned in conjunction with Hunterston developments; this included establishing fairly wide road-side verges (but not footways) – usually 2–3m wide. Because the curvature is gentle and uniform, it is possible to drive along at speed; however, it is not well suited for overtaking at higher speeds, as the curvature limits forward vision. The carriageway width is around 7.0m.

The 1.25km interval to the south is dead straight, and narrower – around 6.56m at the lay-by. The verges are generally narrower, and bordered by hedges / fencing. Some drivers entering this straight stretch see it as an opportunity to overtake; equally, north bound drivers see an overtaking opportunity starting at the B782 junction (at Highthorne).

There is a cluster of serious accidentsjust south of the Kilruskin Road T-junction, where the curved road interval transitions into the straight section; the length of the cluster section is about 220 metres. There is a second cluster of serious accidents at the B782 Highthorne junction. The A78 has a partial blind characteristic at each of these cluster sites.

Hazards and Risks

These are ranked according to the rationale set out in Support Package SP C3

Accident History

Refer to the Summary Maps, which showindividual injury accidents over the last 23 years. The accidents are categorised according to the severity of injuries suffered – slight, serious or fatal. Accident cluster sites are obvious from this map, and there is a clear correlation between these and identified Hazard Areas.

Survey and Hazard Identification

Thisis split into 4 parts:

A78 to north of the Kilruskin Junction
Kilruskin T-Junction
A78 between Kilruskin Junction and the turning into Hunterston Estate
The trio of junctions at Highthorne

Part 1: A78 to north of the Kilruskin Junction

This interval of carriageway is described above under Interval Characterisation. The only apparent hazard is the interface between motor vehicles and cyclists- who do not have a separate Cycle Way (there is no cyclist warning sign). See photos 1 – 5.

Part 2: A78 / KilruskinRoad T-Junction Refer to photos 4, 5 and 6

Carried out November 2011 and December 2012

A78(T) to south of junction (Ardrossan side) / A78(T) to north of junction (Largs side) / Kilruskin Road to east of junction
Road type / Single-lane rural A-road, no central reservation / Single-lane rural A road, no central reservation; was realigned in conjunction with Hunterston developments, including establishing broad side verges (no footways) / Single lane unclassified rural road; width at junction before the bell-mouth is about 20 feet (6m) / Hazard Area 1: Kilruskin Rd / A78 T-junction
Refer to photos 4, 5 & 6
Contributing Factors
The application of the national speed limit (60mph for cars)
Joining the A78 from Kilruskin Road:
+ the line of sight to the left (south) only opens up when about 5m from the junction edge
+ the junction is Give Way rather than Stop
+ traffic joining the A78 has to negotiate 1 or 2 fast-moving traffic flows
+ driver may intend turning without first stopping at the junction
+ There is no restriction on overtaking on the A78
+ The A78 here sees significant numbers of recreational cyclists
Turning right from A78 into Kilruskin Road
+ Driver must cross fast-moving A78 south-bound traffic
+ Driver has no right-turn filter lane
Margin for Error: Low
Hazard Area 1 Ranking: Level 5, Significant
Photo 5: 4.8m from junction edge, looking south along A78; line of sight opening up

Traffic Flows / Steady; broadly equal flows in both directions; most traffic leaving the A78 to join the Kilruskin Road is turning left, having come from the Largs side.
“Rush-hour” traffic (including Hunterston shift changes) adds significantly to traffic flows. / Lighter, broadly equal flows in both directions. More traffic turns right (north towards Hunterston / Largs) than left.
Most traffic entering Kilruskin Road at the junction is turning left (having come from the Hunterston / Largs side)
Condition of carriageway surface / Generally sound / Generally sound
Current Speed Limits / National Speed Limit (60 mph for cars, down to 40mph for heavy trucks)
Speed Considerations / The carriageway contours on the junction approaches mean that 60 mph is not a difficult speed to maintain. / Gauging the speed of approaching traffic from the south is more difficult (traffic is coming almost straight-on to the waiting car due to the slight carriageway curvature).
Gauging the speed of approaching traffic from the north is a little easier due to the approach angle.
Road contours approaching junction / A gentle uniform left curve; generally level / A gentle uniform right curve; generally level / Almost straight (slight curvature to right); downhill
Arrangement of Junction / The junction is divided by an island to separate the 2 traffic flows. The island carries 2 Keep Left signs.
There is a wide bell-mouth.
Lines of sight / The junction is visible when approaching it. It has a reflector post on each side of the bell-mouth. / The line of sight along both directions of the A78 is not good till about 12 yards from the junction at which point the line of sight is established to the right (north); the line of sight to the left (south) only opens up about 4.8 yards from the junction edge.
Roadside Vegetation
Carriageway Markings and Signs approaching the junction / The carriageway has a central hazard warning line, starting about 112 yards from the near edge of the junction, on the south and north approaches.
There is an edge line at both edges of the carriageway.
There are reflectors along both edges of the carriageway and along the centre of the carriageway.
There are no prohibitions on overtaking on the A78 to north and south of the junction
There is a reflector post in the verge on each side of the bell-mouth. / There is a central hazard warning line up to the junction.
There is a give way sign about 20 yards before the junction, and a give way triangle is painted on the carriageway just before the junction.
At the junction, there are double broken lines across the left carriageway (give way at major carriageway), and a single broken line across the rightcarriageway.
There are no town directional signs at the junction.
There is a Direction sign to West Kilbride located about 112 yards short of the junctionto the north and south.
Carriageway Lighting / none / none

Part 3: Mainly straight interval of Carriageway from south of Kilruskin T-junction along to right turn into Hunterston Estate Road – Refer to photos 7 - 12

As stated under Interval Characterisation: This 1.25 km interval to the south is dead straight, and narrower - 6.56m measured at the lay-by. The verges are generally narrower, and bordered by hedges / fencing. Some drivers entering this straight stretch see it as an opportunity to overtake; equally, north bound drivers see an overtaking opportunity starting at the B782 junction at HIghthorne.

There is a cluster of serious accidents at the north end, just south of the Kilruskin Road T-junction, where the curved road interval transitions into the straight section; the length of the cluster section is about 400 metres. At this transition there is a partially blind characteristic.

Hazard Area 2: Partially blind transition and straight interval of A78 from just south of Kilruskin T-junction along to right turn onto Hunterston Estate Road.

See Photos 7 – 10 & 13

Contributing Factors

Singly and in combination:

+ For a driver heading south, there is a blind interval of road in the transition between the curved and straight sections, more pronounced to the driver’s right side of road

+ Encountering an overtaking driver – maybe impatient - and who makes a misjudgement

+ The relative narrowness of the carriageway

+ The national speed limit of 60mph for cars

+ The low margin for error associated with speed and narrow carriageways

+ The zero margin for error associated with vehicles passing in the presence of a cyclist

+ The introduction of a sudden need to brake, coming from traffic appearing from the Kilruskin junction, the Hunterston estate junction, the B782 junction, or over the blind brow at Highthorne – or from the lay-by

+ The compounding of these scenarios when a traffic flow in one direction meets a similar scenario approaching from the opposite direction.

Margin for Error: Low, sometimes none

Hazard Area 2 Ranking: Level7, Serious

Part 4: Survey of Trio of A78 T-Junctions at Hunterston Estate Road, Highthorne Road(B782), and Thirdpart Road

Refer to photos 12 – 27

There is a cluster of serious accidents at the B782 Highthorne and Thirdpart junctions; the road interval is about 220 metres

A78 at south side of B782 junction (from Ardrossan) / A78 at north side of B782 junction (from Largs) / B782 to east of junction (from West Kilbride) / Hazard Area, Contributing Factors, Margin for Error, Hazard Area Ranking
Road Type / Single-lane rural A-carriageway (no central reservation)
The interval of A78 around the B782 junction is around 6.50m wide, and is straight.
There is a blind bend at its southern end (just north of Carlung Farm) and a blind brow and down-slope just north of the junction; the blind brow is not sign-posted
Some north-bound drivers entering this straight stretch see it as an opportunity to overtake, starting at the B782 junction at Highthorne. / Single-lane rural B-carriageway; width at junction is about 6.9m. The carriageway has no markings from West Kilbride till just before the junction. It is characterised by farm accesses (6); field accesses (many); bends, hills; roadside vegetation which includes hedges. The above contribute to limited lines of sight along its length. / Please refer to photo survey and detail from OS Map.
Hazard Area 3: Hunterston Estate Road Junction and adjacent interval of A78
Refer to photos 10 - 13
Contributing Factors
Singly and in combination
+ traffic joining the A78 has to negotiate 1 or 2 fast-moving traffic flows
+ the junction’s proximity to the B782 junction, at which point overtaking is permitted for north-bound A78 traffic; the blind brow contributes to this hazard
+ its position in the A78 south-bound overtaking zone
+ the junction is not sign-posted on the A78
+ there is no right turn filter lane for traffic leaving the A78 at the junction (the carriageway is to narrow to have one)
+ the absence of clear markings and signage at the junction
+ the narrowness of the A78 carriageway reduces margins for error
+ a footway / cycleway crosses the Hunterston Estate Road just short of the A78, obliging drivers turning off the A78 to yield to cyclists / pedestrians
+ on top of the foregoing is the application of the national speed limit – 60 mph for cars
Margin for Error : Very Low
Hazard Area 3 Ranking: Level 7, Serious
Junctions / The three T-junctions are spaced as follows along a 400 yard interval of the A78:

At 257 yards north of the B782 junction is the T-junction on the west to Hunterston Estate
At about 134 yards south of the B782 junction is the T-junction on the west to Thirdpart

The A78signage for these 3 junctions is as follows:
Hunterston WestKilbride Thirdpart
260 yards from B782 (B782) 134 yards from B782
Coming from North no yes yes (added 2012)
Coming from South no yes yes
Traffic Flows / A78 flows are steady, broadly equal flows in both directions. Rush-hour traffic (including from Hunterston power stations) adds significantly to traffic flows.
Of the 3 junctions, the busiest is the B782; the least used is the Hunterston Estate Road. / Lighter, broadly equal flows in both directions; more traffic turns right (north towards Largs) than left.
Most traffic entering the B782 at the junction is turning left (having come from the Hunterston / Largs side). / Hazard Area 4: B782 T-junction and adjacent intervals of A78
Refer to photos: 12 – 17 & 24
Contributing Factors
Singly and in combination
+ traffic joining the A78 has to negotiate 1 or 2 fast-moving traffic flows
+ the partially blind brow at the north side of the junction results in limited lines of sight along the A78 to the north when joining from the B782 – until almost at the junction edge
+ Correspondingly, the junction is partly obscured from about 160 yards to the north; and the junction’s visibility on the approach is not prominent
+ the partially blind brow at the north side of the junction results in A78 traffic approaching from the north being blind to traffic approaching the junction from the south – and vice-versa
+ the status of the junction as Give Way instead of Stop
+ the overtaking restriction for north-bound traffic is lifted at the junction
+ there are no turning filter lanes for traffic leaving the A78 at the junction (the carriageway is not wide enough for these, although the land is there)
+ the width of the A78 carriageway reduces margins for error
+ the presence of cyclists, pedestrians and equestrian users
+ on top of the foregoing is the application of the national speed limit – 60 mph for cars
Margin for Error: Very Low
Hazard Area 4 Ranking: Level 8, Very Serious
Accidents / For the interval of the A78 between Carlung and about 400 yards to the north of the B782 junction, the accident record is bad: there have been several deaths and serious injuries.
There is a cluster of serious accidents at the B782 Highthorne and Thirdpart junctions
Speed Limits / National speed limit, 60 mph for cars, 40mph for heavy trucks / National speed limit
Speed Considerations / The carriageway contours and straightness of this stretch of the A78 mean that 60 mph is not a difficult speed to maintain.
It is common to see traffic flows travelling at 40 mph; but it is also common to see occasional drivers at 60 mph, and overtaking. / Gauging the speed of approaching A78 traffic is not easy; to the north it is made more difficult due to the blind brow at the start of the down-slope.
Carriageway contours approaching junction / Level carriageway up to the junction, then dips downhill; carriageway is straight / Uphill slope towards the junction; carriageway is straight / Level carriageway, final approach is at right angles to the A78. The bell-mouth at the junction allows for vehicles to turn smoothly.
Lines of Sight / A car approaching the B782 junction from the south will find the line of sight along the A78 to the north is impaired immediately north of the junction due to the brow of the hill / A car approaching the junction from the north will find the line of sight along the A78 to the south of the junction impaired due to the brow of the hill / A car at the junction about to join the A78 has clear line of sight to the left (south) when about 10 yards from the junction.
To the right (north) he has clear line of sight only once he is about 1 yard from the junction; however, once he has this line of sight, the down-slope curvature of the carriageway will cut off the lower part of approaching vehicles at a distance of about 160 yards. / Hazard Area 5: Thirdpart T-junction and adjacent intervals of A78
Refer to photos:18 - 27
Contributing Factors
Singly and in combination
+ the absence of clear markings and signage for the junction
+ traffic joining the A78 has to negotiate 1 or 2 fast-moving traffic flows
+ traffic joining the A78 has very restricted line of sight along the A78 to the south –which opens up only when car is 2 yards from carriageway edge
+ the status of the junction as Give Way (?) instead of Stop
+ its proximity to the dogleg bend to the south – 175 yards, which equates to the 55 mph wet-road stopping distance; and to the B782 T-junction to the north
+ the narrowness of the A78 carriageway reduces margins for error
+ there is no right turn filter lane for traffic leaving the A78 at the junction (the carriageway is not wide enough for this)
+ the presence of cyclists, pedestrians and equestrian users; the junction has an A78(T) pavement to left and right.
+ the presence of slower moving agricultural traffic and ‘horse-box’ traffic
+ the slow tight turn for traffic turning left off the A78
+ the bell-mouth at the junction allows for vehicles to turn smoothly, but the narrowness of the Thirdpart road does not allow for 2 vehicles to pass in the immediate vicinity of the junction. Consequently longer vehicles entering the Thirdpart road are required to wait on the A78 to allow an exiting vehicle to clear the junction.
+ on top of the foregoing is the application of the national speed limit – 60 mph for cars
Margin for Error: Very Low
Hazard Area 5 Ranking: Level 8, Very Serious
Roadside Vegetation / Not obscuring the junction / If grass is allowed to grow in the area on the north-east side of the junction, the reduction in the line of sight mentioned above is aggravated.
Carriageway Markings and road signs approaching the junction / The carriageway is marked as follows, from south to north; distances are to the near edge of the B782 junction:
+ solid double white lines up to the junction; at the junction this changes to broken / solid lines, (overtaking permitted heading north)
+ edge lines at both edges of the carriageway up to and beyond the junction
+ reflectors along both edges of the carriageway and down the centre of the carriageway
+ Greenock / Hunterston / West Kilbride direction sign 114 yards before the junction
+ Greenock / Hunterston / West Kilbride direction sign at the junction / The carriageway is marked as follows, from north to south; distances are to the near edge of the B782 junction:
+ edge line at both edges of the carriageway up to and beyond the junction.
+ reflectors along both edges of the carriageway and down the middle of the carriageway.
+ At 345 yards from junction there is a cyclist route warning sign.
+ At 235 and 205 yards, Get-In-to-Left arrows painted on the carriageway
+ At 166 yards, an Irvine / West Kilbride direction sign.
+ At 175 yards, the carriageway centre line changes to solid / broken white lines which continue to the junction (no overtaking heading south); at the B782 junction they change to double solid lines which run up to the far side of the dogleg bend.
+ A left T-junction-ahead sign at 120 yards
+ A white square painted in the middle of each carriageway at 88 yards
+ The word SLOW is painted on the carriageway at about 72 yards
+ A left bend sign at 34 yards, which refers to the dogleg bend beyond the Thirdpart T-junction / + There are no line markings on this carriageway from West Kilbride until about 42 yards before the junction; from this point up to the junction, the centre of the carriageway is marked with a hazard warning line.
+ cyclist route warning sign 100 yards from the junction.
+ 8 yards before the junction there is a Give Way sign, and a white Give Way warning triangle painted on the carriageway.
+ At the junction, there are double broken lines across the left carriageway (give way at major carriageway) and a single broken line across the right carriageway.
+ There are Irvine & Greenock direction signs on the far side of the junction.
Traffic Calming features / Nothing other than stated above / no
Road Lighting / no / no / no
Footways / Yes, on the west side and separated from the carriageway by a 3m (varies) wide grass verge (this footway runs from Seamill to about 400 yards north of the junction). / no
Provision for Cyclists and Pedestrians / + Cyclist Route Ahead warning sign about 50 yards before left turning to Thirdpart
+ A Cyclist and Pedestrian use sign marks the continuation of the footpath on the north side of the Thirdpart T-junction.
+ A Cyclist and Pedestrian direction sign is located on the pavement at the junction / + Cyclist Route Ahead warning sign about 345 yards from the junction. / + Cyclist Route Ahead warning sign about 100 yards from the junction.
+ Sign indicating off-carriageway cycle path about 35 yards from the junction.
+ There is a short cycle-way separated from the carriageway for last few yards of the approach to the junction. A Cyclists Dismount sign is located on this path just short of the A78.
Bus Stops / Unmarked bus stops are in use about 30 yards from the A78
Provision for Horse Riders / Recreational horse riding is popular in this area. Horses are stabled at Thirdpart, and nearby at Millstonford immediately to the north-east of the junction. Riders typically cross the B782 about 30 yards from the A78junction, then pass along the cycle way and cross the A78 to the footway which then gives access to the rural (unclassified) road to Thirdpart.

Risk Assessment