Count Of Drivers

Suhel_Ansari - this should work for both a column and a measure. Just replace Table with your table name:

CALCULATE(COUNTROWS( Table), ALLEXCEPT(Table, Table[Driver Name] ))

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Hi Suhel_Ansari 
Create Calculated column in the Fact_Contracts table

Driver Contract Count = 
CALCULATE(COUNTROWS(Fact_Contracts), ALLEXCEPT(Fact_Contracts, Fact_Contracts[Driver_key]))

and create measure in the Dim_Driver table

Driver Count(M) = 
IF(HASONEVALUE(Fact_Contracts[Driver_key]),
    //True Result
    CALCULATE(COUNTROWS(Fact_Contracts),
        FILTER(ALL(Fact_Contracts),Fact_Contracts[Driver_key] = MAX(Fact_Contracts[Driver_key]))),
    //False Result
    SUMX(VALUES(Fact_Contracts[Driver_key]), CALCULATE(COUNTROWS(Fact_Contracts)))
)

I am also attaching a .pbix file for your reference.
https://drive.google.com/file/d/1MHPeKgVecPhIaFDpby81DQg8G2nbVrgZ/view?usp=sharing

Thanks,
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