The safety of a road surface depends upon the foot hold afforded by it to horses under normal conditions, and also upon the degree of slipperiness that it may take in wet weather, or under the influence of ice and snow in winter.
A dry earth road in good condition gives the best and surest foothold, with broken-stone and gravel roads nearly as good.
The relative safety of the various pavements used in city streets is a matter upon which there is consider able difference of opinion amongst authorities. Local conditions affect the pavement in this regard to an im portant degree. The dampness of the climate, the shade from buildings, the cleanliness of the streets, and the prevalence of snow and ice in winter are all important.
Statistics upon the question of relative safety of wood, asphalt, and granite have been collected by Captain Greene in this country and by Colonel Haywood in London, the attempt being made to deter mine the number of miles traveled by horses upon each kind of pavement to each accident due to slipperiness.
The results of Colonel Haywood seem to show that of the three, wood is the safest and granite the most dangerous, while the results of Captain Greene show asphalt to be the best and wood the worst in this particular.
Colonel Haywood's observations were all taken on London streets, and are as follows: The observations were made when dry weather prevailed, and therefore are somewhat unfavorable to granite, which is safest when wet.
Captain Greene's observations were made in several American cities, and showed the distance traveled to each fall to be, on granite 413 miles, on asphalt miles, and on wood 272 miles. The observations on wood in this series were too few to give a reliable in dication, and it is to be observed with regard to all of them that slipperiness is largely affected by the con dition in which the surface is maintained, and it is therefore difficult to draw any general conclusions which would fit all cases.
All hard pavements are slippery when muddy and wet, and cleanliness is the necessary condition of safety.
Wood and asphalt, if clean, are least slippery when dry and most so when simply damp. Granite, after the surface becomes worn and polished, is most slip pery when dry and least so when wet.
Under a light fall of snow both wood and asphalt become very slippery, and in freezing weather wood sometimes becomes slippery through the freezing of the moisture retained by it.
No statistics are available as to the safety of brick pavements, but it is thought a desirable material in this respect.
It may also be remarked that the danger of a horse falling upon any pavement depends very largely upon the training of the animal and whether he be accus tomed to the particular surface in question.