交通阻塞

• 六(six; intersection)ASSOCIATIVE
• 乂(cross; intersect)PHONETIC

Two diagonal lines crossing like human legs stepping represent intersection and exchange.

• 辶(step; move)RADICAL
• 甬(passage; channel; path)PHONO-SEMANTIC

Following a clear pathway or passageway is the meaning of the character.

• 宀(roof; cover)ASSOCIATIVE
• 土(earth; soil; land)RADICAL

Stuffing earth under a roof to seal all the gaps is what blocks and fills means.