Complex sentence: It starts at its junction with the northern end of Southend's pedestrianised High Street and becomes part of the A13 when it passes Porter's Grange, Southend's Mayoral residence.
Split into simpler sentences: It starts at its junction with the northern end of Southend's pedestrianised High Street. It becomes part of the A13 when it passes Porter's Grange, Southend's Mayoral residence.