What you can comment on

Technical advice (including road safety and traffic)
design and appearance
character of the local area
local, strategic, regional and national planning policies, including the Local Development Plan
adequacy of parking/loading/turning areas including access
highway/pedestrian safety
traffic generation
pollution, noise and odour
sewage and drainage
loss of trees and landscaping
effect on biodiversity and wildlife
impact on listed buildings and conservation areas
loss of light, overshadowing, overlooking, privacy
effect on neighbours, visual amenity

Loss of private view
inconvenience or problems casued by building works (- although I think that this can be raised if you consider that construction will create a safety hazard)
effect on property prices/values
type of resident