Delhi Chief Minister Arvind Kejriwal on Friday said it was not possible to implement the odd-even traffic rationing scheme on a permanent basis."It is not possible to implement the scheme permanently," Kejriwal told CNN-IBN. "These weapons are used on temporary basis to curb dangerous levels of pollution."He said the scheme would be in practice till January 15. "A decision on whether to continue it or not will be taken only after January 15."The odd-even scheme that allows odd and even-numbered private vehicles to ply on the city roads on alternate days aims at reducing air pollution levels. The scheme started here on Friday.