U5 ROAD. 



improvements have been introduced in the systems of construction 



ami repair, the direction and levels have been frequently left unaltered, 



1 the temporary inconvenience and expense attending a devia- 



m the established course. The scanty information we possess 



he state of the roads in early times indicates that it was very 



bad ; and after the introduction of turnpikes, and even down to the 



commencement of the present century, the greater part of the roads 



were, owing to injudicious modes of construction and repair, in a state 



very unfit for traffic. 



inefficiency of the system of maintenance by parish and statute 

 labour was proved before the passing of the first Turnpike Act in 

 yet the necessity of improvement, and the obvious justice 

 of maintaining roads by the produce of tolls, did not lead to the 

 extensive adoption of the turnpike system for about a century after 

 that time. 



During the last sixty years the attention of government has been 



repeatedly directed to the importance of this class of public works, and 



the Highland and Holyhead roads, formed by Telford and others, 



uli in improving and extending the science of road-making. 



I ighland roads alluded to were made under the commission of 



1803, and originated in the military roads formed in consequence of 



the rebellions of 1715 and 1745, which had been found very beneficial 



district* to which they afforded the means of access. The roads 



made and improved under the management of the Highland road 



Commissioners extend to more than 900 miles, the whole being in a 



mountainous district, but so well laid out that their inclinations are 



always moderate. The works executed in the formation of these roads 



are very extensive, and comprise upwards of 1100 bridges. The ll..ly- 



head road improvements were commenced in 1815, and in these 



Telford and his able assistant* had the opportunity of carrying into 



effect, under a government commission, a plan of road-making suitable 



to a great traffic, on principles generally considered to be nearly 



perfect. The principles on which these important works were executed 



are very fully detailed by the late Lord Congleton, then Sir Henry 



Varnell, in his valuable ' Treatise on Roads,' to which work the writer 



of this article is indebted for much of the following information. The 



name of MeAdam must not be [isssed over without notice in this 



place, as his exertions have done much towards attracting public 



attention to the improvement of roads, even where his peculiar prin- 



1 have not been acted upon. 



Though much remains to be accomplished, and the philosophy of 

 rood-making is yet very imperfectly understood by a large proportion 

 !' those to whom the care of the highways is committed, it is im- 

 possible to compare the past and present state of roads without feeling 

 grateful for their improvement, and observing in how great a degree 

 that improvement has benefited the agricultural, commercial, and 

 moral interests of the community. 



Daigning a Lime of Road; Earlk-r'jrlt, <l-e. Though formerly 

 little attended to, the design of the plan of a line of road is a subject 

 which requires extensive knowledge and mature deliberation. It i* 

 often advisable to survey several different lines, in order to the selection 

 of the one which, on careful comparison, appears to have the prepon- 

 derance of desirable qualities. To be theoretically perfect, a road should 

 combine the qualities of straightneM and level, and its surface should 

 be smooth and hard ; and the best road, practically, will be that which 

 makes the best compromise between unavoidable deviations from this 

 theoretical perfection. It may be observed, however, that although 

 some writers speak of the absolute perfection of each of these qualities 

 as Msontisl to the idea of a good road, it may be questioned whether 

 it be desirable of any, excepting of the first Of these qualifications 

 the first two belong to the assign or laying out of the line, and 

 the hat two to the execution of the road and the materials made 



The qualities of stnightnes* and level, or the lime of dlreetioa and 

 line of oVwtBil, should be very carefully adjusted to each other. 

 Some remarks on this subject will be> found in the article RAILWAY, 

 which apply equally to the laying out of common roads, though the 

 proportionate retardation due to a given aftent is very different, owing 

 to the peat comparative resistance of a common road. Among the 

 etraumatancea that may authorise a deviation from the straight line, 

 are the power of obtaining suitable materials for the road, avoiding 

 valuable property or difficult ground, and including towns or villages 

 in the route. 



It seem* to be a prevailing opinion with modem engineers, that the 

 line of direction has not generally been made as subordinate as it 

 should be to the line of draught ; and it will be well to remember, in 

 laying out a new road, that while the effect of gravity must ever 

 remain the same, the resistance occasioned by imperfections in the 

 road and carriages will be reduced by every prospective improvement 

 in their construction ; thereby increasing the proportimale effect of 

 gravity, and making the line of direction still more subordinate to that 

 of draught, or, in other words, increasing the length of level road that 

 may be traversed with the same expenditure of power as would raise 

 the load up a given elevation. Curves increase the resistance to the 

 motion of carriages, and add to the risk of accident ; but if slight, they 

 Inrrmsn the length of the road much less than might be supposed. 

 Edgeworth, in his ' Essay on the Construction of Roads and Carnages,' 

 says, " A road ten miles long, and perfectly straight, can scarcely be 



ROAD. 



120 



found anywhere ; but if such a road could be found, and if it were 

 curved, so as to prevent the eye from seeing farther than a quarter of 

 a mile of it, in any one place, the whole road would not be lengthened 

 more than one hundred and fifty yards." 



The principle explained in the article RAILWAY, of so arranging the 

 inclinations on each side of the summit, or highest point unavoidably 

 passed over, that there may be no unnecessary rise and fall, is equally 

 deserving of attention in the design of a common road, although it has 

 been much neglected. The following statement respecting an old 

 road in the Isle of Anglesey, which was altered by Telford, shows how 

 very much a road may be improved by judicious alterations ; not only 

 by shortening the line and lowering the summits, but also by diminishing 

 the minor undulations : 



Old road 

 New road 



: .- 



Summit above 

 high water. 

 . 339 feet 

 193 



Total rise 

 and fall. 

 3,540 feet 

 2,257 



146 feet 1,283 feet 



Length. 



Milen. Yards. 



24 428 



21 1,590 



592 



However desirable a perfect level may be in theory, a road with 

 moderate inclinations, as of 1 in 100, is found to be preferable in 

 practice, because without such a slope it is difficult to get rid of water 

 fast enough, unless the road be raised a few feet above the surrounding 

 land, and thereby exposed to the free action of sun and wind. Slight 

 undulations are also considered, by most authors, to be desirable in all 

 cases where animal power is employed ; frequent changes in the nature 

 of exertion being considered favourable to the horses. On this 

 principle it is recommended that where an undulating road is reduced 

 to a uniform gradient, occasional levels should be introduced to ease 

 the draught. Any inclination exceeding the angle of repose, or that 

 beyond which a carriage would roll down by its own gravity, occasions 

 a loss of power ; but all below it are attenue<l with a compensating 

 effect when the traffic in both directions is taken into account ; the 

 advantage gained by descending carriages being equal to the additional 

 labour required in the ascent. This angle has been stated by Lardner 

 to be about 1 in 40, with a good carriage on a broken stone road of the 

 best quality; but the inclination allowed on the Holyhead road is 

 1 in 35, a slope which may be ascended at a good rate of speed, and 

 descended at twelve miles an hour without risk. A greater slope not 

 only occasions much additional resistance in the ascent, but, by ren- 

 dering it unsafe to drive down at full speed, causes a loss of time in 

 the descent also. Modern engineers consider it unadvisable in any 

 case to exceed an inclination of 1 in 24, though there are hills at least 

 twice as steep on some turnpike reads. The following table shows the 

 effect of various inclinations in increasing the draught of a stage -mai-h 

 at different velocities on the same description of road, as indieated by 

 a dynamometer contrived by Mr. Macneill for experiments on the 

 draught of carriages : 



Force required at 



It should always be borne in mind that the occurrence of one steep 

 hill "ii a line of road affects the working of the whole stage, as the 

 number of horses required for ascending it must be used, although a 

 portion of their power may be unemployed, on the greater part nf the 

 road. The inconvenience of a steep inclination may l>e diminished by 

 laving a stone tramway for the use of ascending vehicles ; a measure 

 adopted with success on the Holyheaxl road, where, on a slope of a!><>ut 

 1 in 20, the power required to draw a ton was reduced by this means 

 from 294 11*. to 132 Ibs. 



In arranging the works necessary for obtaining the required level, 

 the preference should be given to embankments; ami. wherever it is 

 practicable, the bed of the road should be elevated two feet above the 

 natural level, for the sake of efficient drainage. Tunnels are very 

 rarely introduced on common roads, being very costly, and, when of 

 considerable length, inconvenient from their darkness. \Vheii the 

 road is in an excavation, the side-slopes should never be steeper than 

 two horizontal to one vertical, and it is desirable to have those on the 

 south side three to one ; because, though many materials will stand at 

 steeper inclinations, it is essential to the preservation of the road, and 

 the comfort of horses travelling upon it, that the nun and air should 

 have free access to its surface. Where stone can be readily procured, 

 the erection of walls at the bottom of the slopes gives a neat and 

 finished appearance to the road, and prevents earth, which may be 

 loosened from the sides, from falling into the aide ohanoak or drains. 

 The Highgato Archway road affords an example of the great difficulties 



ThU useful instrument, which its ingenious inventor denominates a Hand 

 Indicator, it mounted on a light phaeton, and beside* marking tlic draught at 

 every ten or twenty yards, points out tlio dintance run, and the rates of 

 acclirlty or declivity on every part of the road. A full description of it is given 

 In Parnell'i ' Treatise on Roads.' 



