The nature of the ground surface has a great effect on energy consumption. Walking on smooth and solid ground is least demanding. The effort increases on a dirt road, gets heavier through light brush, on hard-packed snow, through heavy brush or in a swampy bog. Compared with walking on black top, walking in loose sand takes twice as much energy, in soft snow 20 cm deep it takes three times as much and in 35 cm, four times as much. (Data collected by Kroemer et al., 1994.) Use of a wheelbarrow or other kind of cart for carrying loads can be helpful. The following are the distances that can be covered with a load of 1 tonne on a four-wheeled hand-truck and using up 1050 work kJ:
On a light railway track 850 m
On a good road 700 m
On a bad road 400 m
On a dirt road 150. m