4.
4.1
ACCIDENT REMEDIAL WORKS
The identification and investigation of accident sites, together with the design and implementation of remedial measures is a major part of the Council’s accident reduction strategy. Accident sites are defined as junctions or 100 metre sections of road with five or more personal injury accidents in three years. An empirical “sliding scale” is used to identify longer lengths of road. In 2007 there were 245 accident sites in the county, including 50 on trunk roads. Remedial measures range from minor changes to road signs and carriageway markings, to major schemes such as area traffic calming or new roundabouts. Larger new road and bypass schemes also play a significant role in cutting accidents. Details of the sites treated in 2007 are listed in Appendix 1. The aim of all accident remedial measures is to achieve an accident saving of at least 50% of the cost of the scheme per year. In practice savings can be much higher than this. The cost of accidents to the community is calculated by the Department for Transport. The costs are based on emergency services, hospital costs, lost production, property damage and an allowance for “pain, grief and suffering”. This last element is calculated on a “willingness to pay” basis derived from market research techniques. The costs shown below are based on 2006 prices and values. Average accident costs: Fatal: £1,690,370 Serious: £196,020 Slight: £20,120
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(Source Road Casualties Great Britain: 2006) 4.6 An analysis has been carried out of all the accident remedial schemes undertaken in Cambridgeshire in 2004 for which full data are available. The results of this are shown in Table 4.1, with figures for 1992 to 2003 shown in Appendix 2. Table 4.1 excludes the mass action programmes, which are summarised later in this section. Low cost measures are expected to achieve a much higher return than higher cost measures, and this is borne out by the table. Low cost measures are always considered initially for any site. Higher cost measures are only considered when no low cost measures are appropriate or where low cost measures have not proved effective.
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Table 4.1
Scheme Effectiveness
Number of sites Three Year Accident Savings 26 36 62 Value of 3Year Accident Savings (£,000s) 1653 3031 4684 Scheme costs (£,000s) 104 165 269 First Year Rate of Return 532% 612% 581%
2004
Under £25,000 Over £25,000 Total
19 3 22
The junction of Wisbech Road and Norwood Road is part of an accident cluster site that extends some 600m eastwards along Wisbech Road. Generally the accidents are scattered along the road but there was a cluster of seven injury accidents around this junction over six years. The majority of these incidents involved turning vehicles and as a result of an investigation in sping 2007 a miniroundabout was proposed as an accident remedial measure. A resurfacing scheme was proposed for Wisbech Road for delivery in summer 2007. This was an opportunity to share resources, road closures and traffic management, thereby reducing the overall costs and providing a good quality good value end result. Therefore the design and implementation of the casualty reduction scheme was accelerated and funding found from a combination of minor safety scheme and developer monies. The works were completed in August 2007.
TRAFFIC CALMING 4.8 30 traffic calming schemes targeted at accident reduction have been carried out in Cambridgeshire since 1989. The before and after speed and accident data for the sites not fully reported previously are set out in Table 4.2, with data for the older sites listed in Appendix Two.
13
Table 4.2
Scheme
Traffic Calming Schemes Before and After Monitoring
Date Completed Nov 2004 Feb 2005 March 2005 Sept. 2005 Accidents Change Before After After in accident rate (3 years) Total (months) (Accidents / year) £101,329 6 5 36 -17% £85,000 1 2 34 +112% £39,472 10 5 33 -45% £127,00 8 8 27 +33% Cost
Carlton Way, Cambridge Station Road, Odsey B1102 + B1103 Burwell Ramnoth Road, Wisbech
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20 out of the 25 schemes installed before the end of 2005 show an observed reduction over and above the county average. Overall there has been a highly significant accident reduction of 49% at the treated sites. The 25 schemes have saved a total of 42 accidents per year, over and above the urban accident trend in the rest of the county. This represents an annual saving of £3.8 million at 2005 prices. The total cost of the schemes was £3.9 million (£4.3 million at 2005 prices). There was a disappointing increase in the accident rate on Yaxley Broadway immediately after the scheme was introduced in the summer of 2003. This was probably due to drivers experiencing difficulty in becoming accustomed to the new arrangements. The accident rate for the last three complete years has slowed, but monitoring will continue. Following the initial disappointing increase in accidents at Carlton Way, as reported in the 2005 report, the scheme has been closely monitored. The increase does not appear to have been sustained. There were no injury accidents reported in 2006, and there is one slight injury where the driver struck a parked car in 2007. A number of the accidents in Chesterton High Street after installation of traffic calming are unusual and not related to the road, for example one involved a cyclist hitting a pedestrian on the pavement, in another someone tripped over whilst boarding a stationary bus, another involved a driver being taken ill whilst driving and in one accident a driver in a stationary car opened his door into the path of a cyclist. In 2007 there were two slight injury accidents. The accident record at this site will continue to be monitored. Following an initial disappointing increase in accidents at Ramnoth Road, Wisbech, the scheme will continue to be closely monitored. A scheme has recently been implemented in Sawtry. The physical features, new footway, footway widening works and interactive signs were installed in 2007. Additional street lighting columns, illuminated speed limit signs and white lining on island will be completed in Spring 2008.
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TRAFFIC SIGNAL INSTALLATIONS 4.16 A number of traffic signals have been installed in the county, either wholly or partly on accident grounds. Table 4.3 shows the three-year before and after accident record for those installations completed during 2005, with historical data for schemes implemented between 1994 and 2003 shown in Appendix 2. No schemes were completed in 2004. These 31 traffic signals installed for at least three years have saved 37 accidents per year over and above the County trend. This represents an annual saving of £3.3 million at 2005 prices. The total cost of the 31 installations was just under £3.0 million (£3.2 million at 2005 prices), with annual maintenance costs of £1,400 per site. Traffic Signals Installed on Accident Grounds 2003 Accidents
Junction Previous Control
Give Way Junction Give Way Junction
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Table 4.3
Date Installed
Oct 2005 Sep 2005 0 0
Before ( 3 years) Fat Ser
2 0
After (2 years) Fat
0 0
Slt
5 3
Tot
7 3
Ser
0 0
Slt
2 0
Tot
2 0
Change in accident rate
-57% -100%
A10 / Denny End Road Cambridge St / Longsands Rd St Neots
RURAL ROUNDABOUTS 4.18 Nine rural priority junctions that were accident sites have been converted to roundabouts over the past 12 years. The results are shown in Table A2.5 in Appendix 2. During the three years before construction, there were five fatal, 33 serious and 67 slight accidents in total at the nine sites. During the three years after there have been no recorded fatal accidents and only four serious accidents at the roundabouts, and the annual average number of slight injury accidents has been reduced from 22 to six. The nine schemes have saved 27 injury accidents per year over and above the change in accidents in the rest of the county. Taking account of the reduced severity, this equates to an annual accident saving of £4.8 million at 2005 prices. The total cost of constructing the nine roundabouts was £5.5 million (£6.7 million at 2005 prices). While lower cost remedial measures are always considered for every accident problem, at some sites these measures are not effective. Historically this has been found to be the case at priority junctions on high-speed rural roads with a problem of right turning accidents. Roundabouts can be extremely effective in tackling these often high severity accident problems. However, at between £900,000 to over £2.2 million, these schemes are more expensive than other accident 15
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remedial measures, and funding can be very hard to find. A problem made more acute by successive reductions in highway funding in recent years. 4.23 In 2002 the Major Safety Schemes programme was established with the aim to progress one such scheme every two years, based upon the normal order of costs for a large rural roundabout. There is a need to identify and prioritise a programme of schemes. A number of junctions have been identified at which it was considered that the only fully effective solution would be the provision of a roundabout. All have been the subject of a variety of low cost measures, primarily signing and road marking, which have had some effect. Generally, right turning accidents are a result of the difficulty of judging speed and distance, not a lack of awareness of the hazard. In 2002 when the programme was originally established there were few alternatives to a roundabout for rural junctions with the type of collision history described above. Since this time there have been huge steps forward in technology and the operation of traffic signal, control. They would still not be ideal for widespread use on high speed roads but at sites with a significant injury accident history involving turning vehicles they have been used with great success in reducing collisions and without an unacceptable increase in congestion. Site investigation work around the junction of the A141 / A605 Hobbs Lots, March identified very difficult ground conditions to the east of the junction. Construction of the roundabout without proper remedial work would result in severe subsidence and failure of the road. The remedial work required is very expensive and pushes the total cost to around £2.2 million, which significantly exceeds the available budget. After careful investigation of the possible alternative solutions & taking into account recent advances in technology and experience at other junctions, the council has made a decision to introduce traffic signals to reduce accidents & ease turning movements at the junction. The remaining potential roundabout locations are:- A142 East Fen Drove Soham, A142 Witcham Toll, B1040 Woodhurst Crossroads and A1096 Galley Hill. It is recognised that development of proposals for Galley Hill may be affected by Highways Agency proposals to upgrade the A14. Analysis of the sites is carried out, reviewing the accident records for the last six years and calculating the savings in cost to the community over an assumed life of thirty years. This is a simplified version of the methodology used to assess major road schemes. Further schemes may be identified through continuing accident site studies and, although previously only roundabouts have been put
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forward, it is possible that major schemes of other types, for example bend realignments, could be proposed. 4.30 As these schemes do not pay for themselves as quickly as lower cost schemes and the accident rates tend to fluctuate it is necessary to take a longer view of both the accident record and the pay back period. Review of the remaining schemes together with any new schemes to determine the next priority site has been deferred to May/June 2008. SAFETY AUDITS - PREVENTION BY DESIGN 4.32 The number of audits carried out in the County has risen steadily from 15 in 1991, when the principle of safety audit was introduced in Cambridgeshire, to over 280 in 2007. Whilst it is difficult to accurately measure the effect of safety audit in terms of accidents saved, national research indicates that safety audit may be preventing, over and above scheme implementation, upwards of one casualty per year per site. On that basis the safety audit process in Cambridgeshire saves at least 280 casualties per year thus saving the community some £12.6 million annually at 2005 prices. A comprehensive computer database and information storage and retrieval system has been developed in-house. Each scheme or site has a unique identification number allowing swift access to information about the audit history of individual location. HD 19/03 in Volume 5 Section 2 of the Department for Transport’s Design Manual for Roads and Bridges for any significant works sets out strong guidelines for Safety Audit of the Highways. Whilst only mandatory on trunk roads HD 19/03 represents industry best practice, this gives a framework that ensures our work is professional and of the highest quality. CAMBRIDGE CITY CENTRE SCHEMES St. Andrew’s Street and Hobson Street Environmental and Safety Scheme 4.36 Between February and August 1996 repaving and refurbishment works were undertaken to improve the environment and safety in this busy city centre shopping street. The measures involved the widening of footways and provision of raised crossing areas to establish greater pedestrian domination along with revised parking facilities for buses, taxis, loading and cycles. During the three years before this scheme was implemented, 32 accidents (seven serious and 25 slight) were reported. During the 36
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months after there were 16 accidents (three serious and 13 slight) - a reduction of 50% in accident frequency. 4.39 The scheme retained the existing traffic access restrictions but attempted to discourage illegal vehicular access by street design. Initial traffic surveys indicated a small reduction in overall traffic levels following completion of the scheme, but more recent surveys show an increase in traffic. Further measures to increase pedestrian priority, reduce unlawful traffic levels in St Andrew’s Street and to improve conditions in Hobson’s Street are now being implemented as part of Stage 4 of the Cambridge Core Traffic Scheme. Layout changes in St. Andrew’s Street to reduce congestion caused by the current bus stop layout, accommodate loading will dovetail with city centre retail development (Grand Arcade) and the recent redevelopment of Bradwells Court (now known as Christ’s Lane). King’s Parade Environmental and Safety Scheme 4.41 Environmental enhancement measures to improve conditions for pedestrians and reduce the amount of traffic permitted to use the street commenced in July 1999 and were completed in November that year. The measures involved the repaving and widening of footways, designated parking areas for permit holders, disabled badge holders and hackney carriages only, extending the historic core pedestrian zone to include Senate House Hill and new arrangements to provide better access for cyclists through the bollard closure between Senate House Hill and King’s Parade. The scheme is intended to reduce traffic levels and give more priority to pedestrians. During the six years 1993 to 1998 eleven injury accidents (one fatal, two serious and eight slight) were reported. In the last three years there have been three slight injury accidents. The measures have been reviewed and opinions on the need for further restrictions, possibly using rising bollards to enforce access restrictions, are mixed. As a result, no further action in this respect is currently planned. Parking arrangements have been reviewed and space for loading and unloading, disabled parking and cycle parking has been increased whilst the little used taxi rank has been removed. Bridge Street Experimental Road Closure 4.45 In January 1997 the Jesus Lane – Bridge Street – Magdalene Street corridor was closed to through traffic. Public transport, emergency service vehicles and pedal cycles are exempt from the closure restriction. Through traffic is prevented from using the route by rising bollards across Bridge Street. Exempt motor vehicles have been fitted 18
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with electronic tags to operate the rising bollards and mandatory cycle lanes have been provided to permit cyclists through the closure point. 4.46 The route had a serious accident record, with a particular problem in Magdalene Street. During the three years 1994 to 1996 there were eight serious and 36 slight accidents along this route. Initially there was a disappointing increase in accident frequency following completion of the measures, with one serious and 56 slight accidents in 36 months. Streetscape improvements to enhance the environment were completed in September 2001. The work included measures to further discourage unauthorised vehicles and improvements to provide a separate bollard controlled traffic lane for each direction at the closure point, along with widened footways, enhanced crossing points for pedestrians and a lower speed limit. There has been one slight injury accidents recorded at the rising bollards during the past three years, and the number of accidents along the whole route has reduced from 14 per year between 1994 and 1996 to six per year between 2005 and 2007. Emmanuel Road Closure 4.50 The scheme uses rising bollards in Emmanuel Road to prevent through traffic using the Parkside – Parker Street – Emmanuel Road – Short Street corridor. As with the Bridge Street closure, only buses, taxis and pedal cycles are permitted through the closure point. The route had a serious accident record, with four serious and 34 slight accidents during the three years 1996 to 1998. Monitoring of the accident situation shows a similar problem to Bridge Street with 24 accidents being reported at the rising bollard closure point between 2000 and 2002. Additional signing was provided to advise drivers of the closure restriction, Following a formal review of the scheme by the Cambridge Environment and Transport Area Joint Committee during the summer of 2000, support was given for streetscape improvements. Funds were approved by Environment and Transport Committee for changes to the Four Lamps roundabout and Emmanuel Road – Drummer Street junctions to discourage unauthorised vehicles from using the closure route and to reduce the number of accidents at the closure point itself. The streetscape improvements were started in April 2002 and completed in the following September. Other measures approved following the review are now being implemented through Stage 5 of the Core Traffic Scheme, a new Zebra crossing on Maids Causeway near St. James Street and a 7.5
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tonne weight limit on Maids Causeway between Four Lamps and Elizabeth Road roundabouts. 4.54 In the last 3 years there has been an average of two accidents per year at the closure point and an average of six per year over Emmanuel Road. Silver Street Closure 4.55 A part-day closure scheme with tidal working was introduced in Silver Street in August 2003 with rising bollards installed to enforce the new access restrictions. As part of the scheme, the layout in the wider western end of the street was changed and traffic calming measures introduced along with a 20 mph speed limit along the whole route. The tourist coach drop off and pick up point was relocated nearby in Queen’s Road. A review of the scheme was undertaken in the autumn of 2004 which showed that traffic had reduced by 60%. The annual accident rate in Silver Street, inclusive of its junction with Trumpington Street, for the first sixteen moths after implementation showed an increase from 3.7 accidents per year to 6.8. However, between 2005 and 2007 there was a total of seven slight accidents on Silver Street indicating a downward trend in accident rates. There is no discernible pattern to the accidents at this time. The accident trend on Silver Street and the alternative route will continue to be monitored over the coming years. MASS ACTION Skid Resistant Surfacing and Retexturing 4.58 A programme of retexturing work was carried out at six sites across the county in autumn 2004. Retexturing cleans and revives the texture of the existing road surface without need for the major works associated with resurfacing. It is not a long term solution as the effects would last only a few years, but is effective in the shorter term where the structure of the road is sound and resurfacing on maintenance is not immanent. Two methods were used depending upon the site conditions, Klarewtex and Hydrotexture. Table 4.4 Retexturing Sites
Road No. B1090 C112 B1050 C111 A505 A605 A505 A603 B1095 Date Treated Oct 2004 Oct 2004 Oct 2004 Oct 2004 Oct 2004 Oct 2004 Oct 2004 Oct 2004 Oct 2004
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Name Bend NE of jn to Woodwalton Kings Ripton Road near kart track Bend near School Lane jn, Longstanton Upwood Rd Jn Gravel Pit Hill, Thriplow Goosetree, Elm Vicinity of Pet Cemetery, Thriplow Orwell Hill, Harlton Double bend west of B1040, Farcet
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The before and after accident record for these nine sites is shown in Table 4.5 below. It can be seen that there was a 36% reduction in accidents following retexturing. Table 4.5 Accidents at Retexturing Sites Accidents Before After 3 years 3 years 36 23 Change in Accident frequency -36%
October 2004 – Nine Sites
4.60 The use of coloured and antiskid surfacing as a specific accident remedial measure has reduced in the last two years. It is highly effective in reducing stopping distances, and is used as standard on the approach to any new signal controlled or zebra crossings. However many of suitable sites have already been treated. The products do have a limited lifespan of three to five years, and this is significantly less at high stress sites where type “scrubbing” as a result of vehicles turning is high. Longer lasting solutions such as using standard surfacing containing aggregate with a higher skid resistance is being chosen for some sites. 4.61 In 2006/07 some of the antiskid work involved remedial work renewing existing worn antiskid that had been in place for some years. Whilst this work may be considered primarily maintenance, continued prevention of accidents at these sites is important. TRUNK ROADS - A14 4.62 Table 4.6 shows the accidents for the last ten years on the 77Km of the A14 through Cambridgeshire. Six per cent of all fatal and serious accidents in Cambridgeshire occur on the A14. Table 4.6 Accidents on the A14 in Cambridgeshire
Fatal 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 3 9 5 5 5 3 3 5 2 4 6 Serious 28 28 25 39 26 22 24 32 33 20 20 Slight 136 142 159 179 196 171 178 164 148 140 148 Total 167 179 189 223 227 196 205 201 183 164 174
21
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The three-lane part of the A14 between Bar Hill and Girton is the busiest section of road in the county. Accident and traffic figures for the 21.6 km length between Hinchingbrooke interchange and Girton (excluding these interchanges) are shown in Table 4.7 below. Table 4.7 A14 Hinchingbrooke Interchange to Girton Interchange
ACCIDENTS
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Fat 1 1 1 3 0 0 0 2 0 2 1
Ser 10 7 9 14 13 11 5 15 19 7 6
Slt 52 49 74 79 75 68 77 63 68 73 65
Total 63 57 84 96 88 79 82 80 87 82 72
Monthly Average 5.3 4.8 7.0 8.0 7.3 6.6 6.8 6.7 7.3 6.8 5.9
Average Accident Daily Rate Traffic (Accidents per Flow* Million Vehicle Km) 63,080 0.13 65,540 0.11 67,300 0.16 66,988 0.18 69,658 0.16 70,343 0.14 71,737 0.14 71,864 0.14 72,671 0.15 74,227 0.14 74,511 0.12
• 4.64
Daily Traffic Flow is 24-hour Annual Average Daily Total from automatic traffic counter at Swavesey.
This part of the A14 carries over 15,000 vehicles per day more than it did prior to completion of the A1-M1 link in 1994, and although there are a lot of accidents, the accident rate per vehicle kilometre is not particularly high for a road of this type. The Highways Agency has produced Safety Action Plans for all network areas. These plans will be implemented to improve road safety on trunk roads and thus assist with the reduction of road casualties.
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