The total area of the Union Territory of Delhi is 148,639 ha, out of this 44,777 ha. had been earlier included in urbanisable limits prescribed in the plan. This area as per 1981 census accomodated 54.5 lac urban population.
The balance urban population resided in 17 settlements declared as towns in the 1981 census and Najafgarh & Narela. To accomodate the 122 lac population, a two progned strategy was recommended:

• Increase the population holding capacity of the existing urbanisable limits i.e. Delhi Urban Area (DUA) - 1981. By this way the population holding capacity could be increased to about 82 lacs.
• Extension of present urban limits to the extent necessary i.e. Delhi Urban Area (DUA) - 2001.
  

Studies revealed that in-order to accomodate the balance 40 lac population an extension of DUA - 1981 to the tune of approximately 18,000 - 24,000 ha. was required. This would form DUA-2001 i.e. the proposed urban extension.

The extension plan to accomodate Delhi's changing requirements named as "Urban Extension Plan". This plan was entailed development of three sub-cities namely Rohini, Dwarka, Narela.