- A121 between B176 and A10, Hertfordshire (Grid ref TL355008)
- A121 between A1010 and B176, Hertfordshire (Grid ref TL362004)
- A121 between A121 / A1010 and Hertfordshire boundary, Hertfordshire (Grid ref TL374005)
- A121 between A112 and Essex boundary, Essex (Grid ref TQ382996)
- A121 between A112 and A121 Honey Lane roundabout, Essex (Grid ref TQ389994)
- A121 between A104 and Redbridge boundary, Redbridge (Grid ref TQ406934)
- A121 between A121 main route and Old Shire Lane, Essex (Grid ref TQ406998)
- A121 between Essex boundary and A1168, Essex (Grid ref TQ411946)
- A121 between A104 and A121 Honey Lane roundabout, Essex (Grid ref TQ420994)
- A121 between Baldwin's Hill and A104, Essex (Grid ref TQ429981)
- A121 between A1168 and Baldwin's Hill, Essex (Grid ref TQ430977)