The 3CRR atlas project is part of a more general effort to provide complete statistical information on steep-spectrum radio sources in general and the 3CRR survey in particular.
Differential synchrotron ageing in the extended lobes can account for the former new result.
Infrared studies have also been begun by Eales et al. In such studies effects due to radio power can be separated from effects due to redshift and evolution. Implications of the CJ survey for such tests are discussed by Wilkinson et al.