Three vehicles were reportedly involved in the incident, which has resulted in a partial road closure northbound and slow moving traffic.
One lane was closed due to a stalled vehicle. This has now been cleared but residual delays remain on M23 Southbound from J8 M25 J7 to J9 (Gatwick Airport).
Meanwhile, delays are said to be easing on A27 Old Shoreham Road westbound between A270 Upper Shoreham Road (Southwick / Holmbush turn off) and A2025 Grinstead Lane (Sompting roundabout).
In Chichester, there are minor delays on the Fishbourne roundabout, eastbound between the A27 and Chichester Bypass (Stockbridge roundabout).
There are also slight delays on Whyke roundabout eastbound between A27 Chichester Bypass and the Bognor Bridge roundabout.
In East Sussex, there has been a collision on the A259, between Peacehaven and Newhaven.
South Coast Road is reportedly blocked eastbound between A259 and Ambleside Avenue, with delays increasing in the area.
Meanwhile, Wartling Road is reportedly partly blocked due to a fallen tree around Boreham Lane
In Hastings, B2159 Battle Road is partly blocked due to an accident.
There are also delays on B2123 Falmer Road southbound around Warren Road, with the 'usual delays' up to the lights in the centre of Woodingdean.
Congestion is easing on A27 eastbound between B2123 The Drove (Falmer / Rottingdean junction) and A277 Brighton Road (Ashcombe roundabout).
Traffic remains slow at A277 Brighton Road (Ashcombe roundabout).