"Better sightlines" refers to having a clear and unobstructed view of something, usually an event or a performance, so that you can see everything clearly without anything blocking your view. Full definition
A rolled up facecloth tucked under a breast will often provide the lift and support needed to free a hand and to give better sightlines for mom so she can see what she is doing. (milkontap.com)
Many hills, rivers, lakes and some twisting roads with good sightlines (helps detect law enforcement). (evo.co.uk)
But that also doesn't mean the LC has abandoned its roots, as evidenced by a communicative - yet - comfortable ride and surprisingly good sightlines for a low - slung coupe. (kbb.com)