Evidentiary purposes of improvement plan. In any proceeding in eminent domain evidence of the entire plan of improvement is admissible for the purpose of determining

(1) Value of property taken.

(2) All damages by reason of deprivation of right of access to any highway to be constructed, established or maintained as a throughway.

(3) The damages which, if the property sought to be condemned constitutes a part of a larger parcel, will accrue to the portion not sought to be condemned by reason of its severance from the portion sought to be condemned and by reason of the construction of the improvement in the manner proposed.