Actually the road was closed after 6 p.m. because of the threat of a terrorist attack on the Randenigala dam, not because of the wild elephants. If it was the reason, they would have continued it even after the war. I have used this road at night and didn't even see a single elephant. But it's better to accompany another vehicle, a lorry may be.
On the other hand I have seen wild elephants beside the road near Thabbowa lake on Puttalam -Anuradhapura road around 1 a. m. ,but I was travelling by a bus. This crazy bus driver even stopped the bus to show the elephants to the few passengers who were awaken at that time. A lady was so mad at him and screamed to move the bus from there.