Track renewals handback at 140mph

Bob Clarke

In 1985, British Rail was moving to a market/business led structure in which sector managers had a budgetary control and were required to grow their business. For the Inter-City sector, journey time improvements were high on the agenda. Electrification of the East Coast Main Line (ECML) was underway with a service introduction planned for the early 1990s. However, at current linespeeds, the reduced journey time with Class 91 electric traction was only to be six minutes better than the diesel HST’s which had better acceleration at lower speeds.

Since the mid-1970s, Brian Davis, chief civil engineer of the Eastern Region (ER) considered every ECML track renewal job and whether the additional cost of line speed improvement could be justified. Hence, many routine track renewals were delivered at an increased line speed. Some locations needed nothing more than recanting and fine lining. More significant work included moving the River Great Ouse at Offord to ease five curves. Also, the major track layout simplification at York and Newcastle increased entry and exit speeds from 15mph to 40mph delivering a four-minute journey time improvement.

However, the total benefit was not enough for a limited stop sub-four-hour journey time between London and Edinburgh.

50mph handback

I was appointed as the ER’s planning and resources engineer in 1985. This introduced me to the possession and Temporary Speed Restriction (TSR) constraints on the operational railway. Management of ‘The Rules of the Route’ process, in conjunction with the ER Operations team led by Colin McKeever and assistant Bill Robinson, optimised an intensely worked mixed traffic railway against the demands of cost effective, safe, reliable maintenance and renewals. The possession regime and planned TSRs for each route were typically considered 18 months ahead for timetabling to reconcile these competing demands.

In the summer of 1985, the Up Fast between Connington and Huntingdon was to have a complete track renewal to provide near perfect track quality. During the week-long block for this work, all southbound traffic used the Up Slow.

All the latest technology was applied during this block including a well-controlled cut using laser technology to give a uniform ballast depth of 375mm, double-tamped to as-near-perfect geometry. Although this ‘should’ settle and compact uniformly under traffic, in reality, track doesn’t settle uniformly and a back-up tamping after one week was necessary. The conclusion was that, on uncompacted ballast, the upper limit of a safe hand-back speed to operational traffic is 50mph however thoroughly the track was tamped.

This is because tamping, however well done, simply corrects the geometry with uniform quantities of ballast forced beneath the sleepers to fill, as far as possible, the void created. Any compaction is limited to 100mm below sleeper soffit and is longitudinal rather than providing vertical compaction. Hence, a higher hand-back speed following ballast cleaning requires ballast to be compacted using a rail-borne machine that simulates substantial traffic volumes.

Dynamic Track Stabiliser

In 1986, during a visit to Austrian Railways to assess High Output Track relaying plant, I, by chance, was introduced to the Dynamic Track Stabiliser (DTS). I realised that this would enable a much higher hand-back speed when following a tamper.

The DTS was developed in the early 1970s as a joint venture between SNCF and Plasser & Theurer. SNCF wanted to do more tamping during warmer weather, as rules limited work when rail temperatures were forecast to rise and increase the risk of track buckling because of a loss of lateral resistance between the sleeper soffit and ballast. (60% of the lateral resistance to buckling is at this interface). Tamping significantly reduces this lateral resistance which is only re-established after the track settles once a substantial amount of traffic has passed.

The DTS was developed to follow the tamper and exert a forward moving and oscillating vertical load equivalent to around 100,000 tonnes of rail traffic with each pass. This enabled SNCF to significantly increase its maintenance tamping mileage each year.
Around this time, British Rail was pioneering its tilting Advanced Passenger Train (APT). Tilt maintained passenger comfort as the APT went through curves at increased speed. However, this doubled the lateral track forces. Hence, use of a DTS following routine maintenance tamping was considered to be essential. As a result, British Rail purchased an early DTS-32N for use coupled to and controlled from a conventional 07 tamper as a slave unit. However, after the APT programme was abandoned, the DTS 32N was never used by the London Midland Region.

After my trip to Austria, I became the permanent way engineering assistant to the Leeds area civil engineer, Morris Smith. I then contacted the London Midland Region area civil engineer to arrange a swap of one of my tampers for his DTS-32N coupled to a 07 tamper. Although this DTS was in poor condition after many years of disuse, Alastair Sugden, who headed the Eastern Region ‘On-track plant maintenance unit’, managed to get it back to full working order.

70mph handback

This DTS and its ballast compacting qualities was first tested on the Up Slow just north of Thirsk on the ECML. With the support of the Inter City East Coast Sector manager, Simon Fraser, and Bill Robinson in Operations, I negotiated a five-day mid-week possession of the Up Slow to trial the DTS.

The Up Slow carried considerable freight traffic with 25-tonne axle loads and local passenger traffic at a line speed of 70mph. It required full depth ballast cleaning to 375mm below sleeper soffit which needed ballast to be compacted in three equal layers of 125mm. The site was cleaned by the routine method using an RM74 machine with the ballast return providing much of the bottom layer.

Fresh clean ballast was unloaded using ‘sea lion’ wagons and use of a ‘shark’ plough to ensure a 125mm layer of ballast. This was then tamped to provide an initial geometry acceptable for the engineering trains and on-track-plant, but importantly to provide as near as possible uniform quantities of ballast beneath the sleepers. The ballast was then compacted using the DTS.

A second pass of sea lions provided sufficient ballast for the second 125mm lift. Two passes of the tamper took the track to the second level on a further 125mm of ballast ensuring as far as possible uniform volumes of ballast beneath sleeper. Then a second pass of the DTS compacted the second layer.

Finally, a third pass of sea lions with shark plough and ballast regulation ensured a fully ballasted track section. This was then followed by a third pass of the DTS.

At this stage, the ballast had been substantially compacted but the geometry was not at the required standard for a 125mph line speed PSR. Therefore, the site was tamped once again to allow for final settlement applying a ‘design overlift’ to achieve excellent geometry on substantially compacted ballast following a final pass of the DTS.

The site was opened with a PSR of 70mph and was visited at regular intervals by the local permanent way supervisor. No residual settlement occurred for many months.

Ballast clean 125mph handback

This first trial proved this basic methodology and enabled hand-back speeds of at least 70mph to be routinely achieved with our plant.
At this point I enlisted the help of David Johnson and his team at Derby Research. Their help was invaluable in providing detailed geometry deterioration and track settlement rates.

The second site chosen was the 125mph Down Fast north of Thirsk. This required lifts of up to 100mm to improve the overall geometry ahead of the route’s electrification. A single pass of stone train, tamper, regulator, and DTS resulted in a finished quality that was handed back to traffic at 100mph. The speed was lifted to 125mph after one week with no further work required. By now it was clear that the basic methodology was sound and that we should be aiming for a 125mph hand-back speed following ballast cleaning.

At this time, the Inter-City director, Dr John Prideaux, wished to achieve a limited stop, sub-four-hour journey time between London and Edinburgh, so an order was placed with Plasser & Theurer for nine DTS-62N machines for both the East and West coast routes. This order was ‘fast tracked’ so that trials with DTS-62N machines on the ECML track could start during summer 1987.

At this time there was a timetabled 21-minute engineering allowance between London Kings Cross and Edinburgh. This gave an average of six items of work with planned 20mph TSRs. (6 x 3.5 minutes = 21 minutes). Hence, if all the plain line track renewals were handed back at line speed this allowance could be reduced to just six minutes for other work enabling the journey time to be reduced by 15 minutes.

Trials with these new DTS machines started in August 1987 at Balne, between York and Doncaster, which had a 125mph line speed. The work was ballast cleaning on the Up Line. To minimise possession time ballast was lifted and compact in two unequal layers instead of the normal three equal. It was felt that this would still achieve the highest quality of geometry upon substantially compacted ballast.

Having a bottom ballast layer of around 250mm followed by a layer of 125mm double tamped, regulated and compacted using the DTS-62N provided a good-quality result. The DTS traces confirmed both geometric quality and that the machine had provided the compaction required, simulating around 100,000 tonnes of traffic with each pass. Hence, Balne saw the first hand-back to traffic at 125 mph. This sustained a high standard of geometry for several weeks before follow-up tamping was required.

This was a resounding success.

Track renewal 125 mph handback

The next step was a complete track renewal on the ECML where the line speed PSR was 125mph. Planning this in a way that could be routinely repeated week after week was a demanding task and a huge credit to the Leeds Track Renewals team led by Richard Thornton.

Given the potential journey time savings from these trials, Inter-City East Coast sector director, Simon Fraser and operations manager Bill Robinson agreed a sequence of weekend 40-hour Fast Line possessions to undertake the work (14:00 Saturday – 06:00 Monday). The first of these was for the renewal of Up Fast at Sessay, south of Thirsk. This job would test the engineering methodology to complete successive 800-yard track renewals with ballast cleaning, which would be handed back on Monday mornings at 125mph.

After much deliberation, Richard Thornton and his team concluded that it was best to relay the sleepers loose, ahead of the rail renewal and ballast cleaning. The 125mph handback required all aspects of the job, including stressing, to be completed prior to handback by to the local PWME, Roger Freeman, who carried the safety of line responsibility. This needed a production line approach. Ahead of the possession, the only work required was the laying of the 600-foot lengths of welded rail in the 10-foot and 6-foot space.

Existing track was removed in flame-cut 60-foot panels. New sleepers were laid loose by a twin-jib track layer. Ballast undulations from the removed track panels needed levelling before new rail could be clipped to the new sleepers. This was done by a BRUFF grader which was profiled to create an upstand beneath the rail seat of the newly laid sleepers.

The new welded rail was then fed into the sleeper housing using rail threaders and clipped down using Permaclippers before being thermit welded. An RM74 ballast cleaner then discharged spoil into open wagons on the adjacent line. Stone trains of sea lions and shark brakes followed, discharging measured quantities of fresh ballast. Jaka Paka’s followed providing a track lift to some 150mm below final design level.

An 07 tamper’s first pass provided good initial geometry, though its main purpose was to compress uniform quantities of ballast beneath each sleeper, by double tamping. A regulator with brush followed to provide a more even distribution of ballast. The DTS then provided a maximum vertical rail loading of around 30 tonnes, operating frequency of 45Hz and at a steady 500 metres per hour. This compacted the ballast by simulating around 100,000 tonnes of traffic.

Two further runs of stone trains with shark brakes followed by the tamper, regulator, and DTS brought the track up to final design level. With the inevitable small undulations in the vertical geometry, a fourth tamper pass allowed for final settlement by applying a ‘design overlift’ to achieve the highest standard of geometry on substantially compacted ballast following a final pass of the DTS.

Rails were stressed and the site tidied for inspection by the PWME during the final hours of the possession to enable PWME, Roger Freeman, to hand-back to operational traffic at 125mph. The Leeds Area engineers team then went on to repeat many further ballast cleaning and complete renewal jobs handing back to operational traffic at ‘Line Speed’ while fine tuning this methodology.

In October 1987, I was promoted to the area civil engineers post at London Kings Cross / Peterborough with an objective of introducing 125mph handback at the southern end of the ECML. This had a higher density of traffic and was thus greater value to the Inter-City business.

Under the guiding mind of Area Permanent Way Engineer] Alex Turner, his ‘can-do’ team considered how to improve upon the standard set by the Leeds track renewal team. To do so they selected ballast cleaning and track renewals in extended weekend possessions between September and December 1988. During this work, the enthusiastic renewals team adopted a variety of methodologies to suit particular site and track conditions.

140mph handback

Many of the renewal sites were on the 20 miles of four track main line between Stoke summit and Werrington Junction. This downhill ‘race track’ had seen 4472 ‘Flying Scotsman’ become the first locomotive to reach 100mph in 1934 and A4 Pacific ‘Mallard’ achieve the 126mph steam traction world record in 1938.

This section of track was also to be used to test run the new Class 91 – 225 electrics at 140mph. This required signals on this section to have a fifth flashing green signalling aspect to provide the required additional braking distance. Hence, rack renewals during this period had to be safe for 140mph running.

One such track renewal was on the Up Fast at Swayfield due to the deteriorating condition of hardwood Jarrah sleepers. This work commenced with the ballast cleaner discharging spoil into open wagons on the adjacent Down Fast line. A pair of Jaka Paka’s followed to provide a geometry good enough for the regulator to grade and brush the surplus ballast clear for the rail to be unclipped and cut into 300-foot lengths for ‘side loading’ onto the adjacent flat wagons for re-use. Jarrah sleepers were then dug out of the ballast using Hymac excavators and loaded loose into open wagons.

The BRUFF grader followed, levelling the ballast, and creating a uniform upstand in the ballast onto which the new concrete sleepers would be placed. A rail threader was then used to move the new 600-foot lengths of LWR into the rail seats of the new concrete sleepers and the rail subsequently clipped down. The rail was then welded.

A stone train, tamper, regulator and DTS followed to provide the next track lift, ensure there was uniform ballast quantities beneath the sleepers, make geometry corrections, grade the ballast profile, and compact the ballast. This was repeated until the track was fully ballasted, regulated, and geometry corrected to the highest standard on compacted ballast to enable the track to be handed back traffic at 140mph following the destressing and site clearance.

As an example, during the weekend of 5-7 November 1988, the 40-hour possession of the Down and Up Fast lines from 14:00 hrs Saturday until 06.00 on Monday completed 700 yards of track and handed it back to traffic safe for 140mph.

Profit centre lesson

Looking back to those very ‘heady days’ of the late 1980s, during just a very brief two/three-year period, it is important to reflect on the achievement and that which had enabled it.

Without doubt, the Area Track Renewal teams at Leeds and Peterborough rose to the challenge to apply their considerable experience and ‘can-do’ approach. The Area Renewals teams at Doncaster and Newcastle also achieved similar results. Thus, all the ECML services benefited from improved journey times.

The Inter-City business was led by Director Dr John Prideaux who made it clear that reduced ECML journey times offered significant revenue benefit. His support was essential and included the ‘fast track’ purchase of DTS machines and granting of extended weekend possessions. This enabled the track renewals teams to develop business-led engineering solutions.

John Nelson, who was the Eastern Region’s general manager at this time, later reflected upon his experience to conclude that:
Railways operate best when they are market driven and when bottom-line responsibility exists at profit centre or business level.
Railway finances, operating performance, and productivity are optimised when marketing and production activities are aligned under single business leadership at the optimum level that is closest to the customer.

Railway operators and engineers work well when they are accountable to, or within, businesses in which they can use their innovative and technical abilities to meet business needs.

Thus, while this story of achieving high-speed handbacks is almost 40 years old, the lessons from it have huge relevance today.
Bob Clarke started his railway career in 1967 as a technical permanent way maintenance assistant in Birmingham. After various posts in British Rail, including those mentioned in this article, he became infrastructure manager Inter-City East Coast and then held director positions at Railtrack and Jarvis. This was followed by consultancy work from 2001 to the present date.

This is an edited version of Bob’s feature which appeared in the October 2024 PWI Journal and is published by kind permission of the Permanent Way Institution.