|In 1998, Osaka City became the first municipality in the country to
apply water-retentive pavement technology to roads as part of measures
to deal with the heat island phenomenon.
Water-retentive pavement is designed to facilitate the storage of rainwater
by forming gaps at frequent intervals in asphalt-based pavement and embedding
water-retentive material for water storage in these gaps. This enables
the storage of 3-5 liters of water per square meter of pavement. As this
water evaporates into the air, it absorbs the surrounding heat and lowers
the surface temperature by about ten degrees Celsius relative to conventional
asphalt. Preventing surface temperatures from getting too hot is the way
in which this innovative new type of pavement helps to diminish the heat
island phenomenon and moderate the heat felt by roadside residents.