National Archives 2003-06-12
Arrived at PRO much as usual.
This file has covering dates 1967-69 and covers the general issue of metricating traffic signs. This breaks down into two parts: metricating the dimensions, which is purely a matter of manufacture and specification in Regulations, and is generally unnoticeable to the driver, and metricating the indications, which affects any sign containing distance or speed units and so is very visible to the driver. The file contains:
• One or two position papers explaining the pros and cons of both types of metrication, generally referring to dimensional metrication as a simple administrative change with no good counterarguments, and indication metrication as a major policy decision requiring Ministerial involvement. • Correspondence between the Ministry, ARTSM, and steel and aluminium plate manufacturers discussing standard sizes in imperial vs metric, how to schedule a dimensional changeover so as to put minimum cost on the traffic sign maker community, and the ARTSM’s reaction to the Ministry’s proposals to make sign designs fully scalable even if this means using letters of non-standard height on signs at certain sizes. (The ARTSM hated the idea apparently because it meant photoreproduction rather than using standard-sized letters. This may be why word-message signs like “Ford” and “Try your brakes” seem to have become much less common after metricated Regs were issued in 1975. • Tables of the MOT’s recommended Imperial Metric hard conversions.
This contains laboratory reports generated by Dr Charlesworth’s unit at RRL (Traffic & Safety). Covering dates January-March 1956, BR423 through BR446. Following reports are of interest.
• BR423—Pacey on behavior of a bunch of vehicles released from a traffic light (does diffusion or kinematics best explain the flow pattern resulting?). • BR424—Economic assessment of priorities for road improvement. Cites a 1952 study by Coburn which relates speed, accident, and layout using Bucks data. (There seems not to be much hope of finding direct research on highway capacity. They seem to have been content to work indirectly, without developing a HCM as such, and instead deriving tabulatable speed/flow/layout relationships.) Contains much interesting information regarding relationship between curvature degree and accident frequency—for instance, a table relates personal-injury accident frequency per 100 MVM to degrees of curvature, with accident rate staying between 2.5 and 4 for curves under 10°, and then rising sharply to more than 13 for curves over 10°. Why such a “knee” to the curve? (Remember, based on Bucks data.) (Coburn study published 1952 as Lab note RN 1827. Similar research on A5 published as Lab note RN 2411 in 1955, and compares 24” and 30” carriageways.) Also, Coburn’s Bucks research showed that accidents dropped 4% for each 1” increase in carriageway width (on a 2-lane road) between 16” and 24”. (Result: it seems obvious that 12” was chosen as a standard lane width for motorways because it represented the point of diminishing returns on further widening. But the data on accident frequency on curves is very provocative. It of course suggests that 2° was adopted as the maximum curvature on British motorways because it also represents the point of diminishing returns on further curve straightening. But was this in fact so? Were computations carried out to somehow relate the cost of a flatter curve standard to the additional earth-moving that would be required and the more stringent alignment constraint that would result? And why did the US choose 3.5° as a maximum curvature figure for the same speed? Did US data relating accident frequency to curve radius follow the same trend as the British data? How often and in what types of terrain did curvature approach the maximum? Was the choice of 3.5° based on some kind of calculation as to the costs of earthworks etc. implied by a more rigorous standard which “traded off” on estimates of the unit costs associated with road casualties? [Cf. a book I found at Farrell Library many years ago which cited $265,000 as one estimate of the cost of a human life. Of course there is more recent cost-of-life data, eg Britain’s HEN series.] Or was the actual effect of a higher maximum curvature modified or mitigated by different rules or informal expectations [unwritten knowledge, part of the American civil engineers’ technological paradigm] to be observed on projects threatening to approach the maximum curvature from below? Gee, there’s a major econometrics PhD thesis right here in studying the specific cost tradeoffs associated with various design standards, even taking the strategic planning framework as a “given,” and with the main thesis topic being: “Why do standards for similar types of roads vary so much between countries and why are the recommended treatments packaged differently?” This thesis would have to look at the extent to which the different standards were influenced by different crash data, and by the different demographic/distributional characteristics of the vehicle fleets in various countries and its different performance characteristics. Is the British vehicle fleet really more diverse than America’s, and can this be proved by deconstructing American and British vehicle statistics with their different simplifications, and can it then be shown that salient differences in design standards and actual construction accomplishment are related to obvious differences in fleet—e.g. can it be said that Britain has a “milk float” roadsystem?) • BR426—Wardrop on tests on weaving sections of large roundabouts. Interesting roundabout configurations were explored, on a test-track at Northolt. • BR427—Coburn and Wardrop on “The importance of speed-flow relationships in studying the capacity of roads”—probably the only explicitly capacity-related paper in the entire RRL archive corpus, and of course it cites the HCM. The abstract gives an indication of why Britain developed a disdain for the operations research/systems analysis approach of the HCM: theoretical capacities derived from a priori computations of vehicle speed and distribution often proved drastically unrealistic (unattainable, even) in ordinary practice, and PIARC-sponsored, non-HCM approaches focusing on “traffic interference” (the extent to which the individual driver’s choice of speed or position is constrained above a certain minimum extent by the presence of other vehicles, expressed as a percentage of “interfered-with” vehicles in the traffic stream) had the central defect that they did not quantify the amount of interference per vehicle. The approach preferred by the RRL was apparently to ignore formal questions of capacity altogether, and analyze empirically derived speed-flow relationships to identify levels and types of traffic density beyond which structural expansion of capacity would yield a positive rate of return on investment. The general idea was that if it paid to widen the road, the road was carrying more than its practical capacity. (The problem with this is that capacity is basically the same for same geometric layouts, but the cost of adding capacity varies radically from one location to another regardless of layout.) • BR429—Slough experiment report no. 30. • BR430—Accidents on A40 in Oxfordshire. • BR434—The committee on road layout decides to rename itself the committee on traffic engineering. (This was strictly a RRL committee, not MOT.) • BR436—Includes a nomogram to help LA traffic engineers determine whether a road is undesirably skiddy (ie has more skids than the lowest easily achievable skid rate for similar locations, based on 1 in 40 statistical significance tests), and needs an anti-skid treatment. • BR441—Harris on “A suggested specification for reflectorising materials used in traffic signs.” The basic research problem is to determine a point at which legibility begins to fall off as brightness increases. (Is microprismatic sheeting beyond this point?) March 1956.
Dammit, I like these RRL reports—a chance to see a discipline (set of paradigmatic knowledge) being built brick by brick.
This file is largely concerned with HEU’s (apparently a daughter division of HE) attempts to come up with a set of speed-flow relationships for incorporation into the COBA manual being prepared. Covering dates 1968-73. Some issues discussed:
• How to treat junctions where the traffic levels exceeded acceptable capacity only during the peak hour • How to respond to/model an apparent secular-trend increase in speeds (owing largely to improved vehicle design) which was making itself manifest in rural areas but was being counterbalanced in urban areas by flow increases • How to adapt the COBA model to treat the “Sunday drivers”: people who are voluntarily choosing not to go at the computed (safe) free speed because they are on a scenic alternative to motorways, have cut out of the motorways because they think motorway driving is “boring,” and want to move at a pace that allows them to enjoy the scenery.
Plus, there is much theoretical discussion about the merits of ignoring capacity in favor of explicit traffic-based economic COBA appraisal—the approach suggested by Coburn appears to have been adopted and to have become established policy but of course this decision was revisited many times.
MUCH in this file worth copying, although it is not clear how the discussions contained herein relate to the decision (taken in 1972-73) to increase design flows.
This file contains plans (many of them drawn up by Freeman Fox & Partners for an unclimbable fence to be used as the bridge railing) for a major bridge over the River Thames on the M4 Maidenhead bypass, as well as a draft bridge specification and bill of quantities drawn up by Scott Wilson Kirkpatrick.
This file contains correspondence between the MOT, LAs, and Gibb & Partners about the Chiswick-Langley flyover (known formally as the London-South Wales Motorway (Brentford-Langley section) Special Road Scheme). In fact it is exclusively correspondence and loose minutes except for a bound report from Gibb giving cross-section, layout, and cost details for several viaduct options. Evidently the route fixed in a planning document (called the “Development Plan,” but which one—the one specifying the Development Areas, or roads in London?) had called for a routing at grade which would have claimed 93 houses and increased severance to an extent where the Ministry of Housing and Local Government felt that the greenbelt would be invaded by development. (They felt the situation was on a knife edge even without the motorway, although the MOT disagreed and hoped MAFF would come on its side.) Evidently, after Gibb had done a feasibility study, a viaduct option was chosen which would support 70 MPH for most of its length, but drop down to 50 and then 40 MPH at the Brentford end, and much of the remaining discussion focused on how to avoid expensive factories while still keeping the geometric standards high. Beechams were successful in getting a sharper (3° rather than 2°) curve added in their area to take viaduct footings away from the pavement outside their office building, while Gibb gave serious thought to acquiring and demolishing factories which would have had to be “flown over” otherwise—for Macleans and Alltools this would have saved about £1.1m in engineering costs but also imposed heavy land acquisition costs, which perhaps explains why these do not seem to have been done.
This is strictly a planning (in the US, environmental documentation stage) file. Construction files come later, and include the files covering the steelwork issues on the Boston Manor flyover bridges. Covering dates 1958-60.
This Welsh office file (covering dates 1964-69) is taken up with the use of the travel and accident loss index as a planning tool for determining which roads need improving, which is then combined with COBA assessment to determine whether the proposed improvement scheme delivers improvement at an acceptable rate of return. Schemes for roads that do not meet COBA are returned for redesign to a lower standard.
The Welsh Office concern was that road schemes in Wales cost £1m per mile, versus £500k in England and £400k in Scotland, and this could result in road improvements in Wales being postponed due to less favourable COBA ratings than English schemes/being referred down for redesign to lower standards/Wales getting overall a smaller share of govt expenditure on roads.
This is an interesting file . . . Principal players (correspondents) are AS Coombs, formerly of St Chris House but now at Welsh Office (Hwys Directorate), and his colleague Brain, at MOT. There are also research papers (preprints mostly) and descriptions of the proposed scheme appraisal procedure and its likely impacts on allocation and equity.
[computer crashed after screen turned off; rebooted]
This file concerns a proposal by AET Matthews (a consulting architect out of Kingston) to construct six “tunnel routes” or “underways” under central London which would have four lanes in each direction and would have nine interchanges, laid out in a grid, underneath the Thames. The tunnels would be buried 80’ or more beneath ground level to avoid existing railway tunnels (to keep the line smooth) and would have attached underground parking garages/bus stations/etc. so that people would just leave their cars parked underground—interchanges with the surface would then be by a complex system of Travelators, escalators, elevators etc. The underways would connect with the motorway network outside central London. The tunnels would be in the clay layer underlaying London, which runs up to 300’ below ground level.
The file contains MOT and RRL correspondence regarding the tunnel proposals, mainly concerned with addressing the question of cost and several Parliamentary Questions directed at them asking why the tunnel proposals were not being taken more seriously. The MOT felt that the projected £4bn cost was too much, impossible to obtain using conventional road financing methods, and the project was unlikely to be toll-viable; using a £7bn surface motorway system as a comparator was not valid, because no such motorway system was proposed, and even if it were, it could probably be constructed at half the cost, while the tunnel proposals would probably cost twice as much; it was bad public policy to build road tunnels instead of using demand restraint to encourage people onto PT, because cars were the least efficient use of roadspace/tunnel volume; the tunnels would still cause problems with tall buildings (possible subsidence and weakening/stressing of foundations) and possibly also with private residences, and might result in the Minister having to pay to acquire land on the surface anyway rather than just the substratum rights. Ventilation was another major problem area, with surface land acquisition being required for stacks, and possible noise and safety issues involved which would not necessarily be mitigated by use of longitudinal venting methods. All in all, many objections were raised, some of which are valid, and others which appear to have been manufactured in order to avoid having existing schemes derailed (such as the GLC’s motorway box and the Ringway proposals). Chief among the latter appear to be the claim of high per-mile costs, which according to RRL research varied very considerably due to the rock being passed through and were moreover dropping in real terms (rivers expensive to cross because compressed air required, but chalk very easy to drill through—RRL found price ranges of £2.1m to £9m per mile for a simple two-lane tube, these being 1972 figures).
All of this said, the Ministry did have two policy committees looking at this issue—an Urban Motorways Committee and a Tunnelling Committee. (I think; or it could perhaps be the Urban M’ways C’ttee looking at tunnelling issues.)
This file (covering dates 1964-66) is 2nd order and deals with the woe caused by the Crindau tunnels on the Newport BP (test borings did not find faulting, so that was found by the tunnel contractor on the main tunnel works, which resulted in delay, expense, requirement to maneuver a tunnelling shield in place, and need to buy properties on Brynglass Road on the surface—much mention of this also made in the London tunnel motorways file). Also, the Newport BP contractors were the cowboys from hell: didn’t maintain diversions or temporary roadways (some of which crossed motorway mainline) and damaged pavements by parking their lorries on them.
Defective clock interfered with pacing and so I didn’t get to view this. Saving it for next time.