This political factor in the modification of roads, the negative and positive effect of legal restraint, works in an opposite fashion to that we have just examined. The older, the wealthier, the more complex a civilization the _less_ this modifying factor is present. Thus in England for many centuries we had no compulsory power in the hands of public authority for the making of a new road. Such powers are, as we shall see when we come to the story of the English Road, a comparatively modern development. On this account the Road was, until modern legislation brought in a new system, compelled to follow existing established ways. It could not even be broadened, let alone a new trajectory enforced; and the only compulsory powers in the hands of the authorities were those permitting the levying of labour, and later of money, for repair. The same is true of the second form of legal restraint, though in lesser degree. Privilege (such as the deflection of an old line of road by Act of Parliament in order, for instance, to add to the privacy of a park--there were not a few examples of this some generations ago) and the positive legal restraint imposed by existing right of ownership obviously decay _pari passu_ with the development of public powers for driving new roads or broadening existing ones. The third political factor modifying the trajectory of roads is that of a variety of objects imposed upon communications by varied social uses. As society grows more complex and at the same time wealthier, as new centres of population arise, new forms of travel and new needs to be satisfied by travel, the simple formula of the line of least effort from one point to another suffers increasing modification. You have to consider not only the line of least effort between two terminals, but the due weight to be given to intervening points which do not lie precisely upon that line. As a rule, of course, these new centres exercise their pressure or attraction automatically, and you get a deflection arising not from plan but from gradual necessity. The same thing happens with new needs (as, commerce replacing arms), but it is curious to note how slowly the modification takes place.