Streetlights are OK, but headlights are better. An animal or other obstruction will only appear as a shadow against a glowing roadway.
Headlights are not better. Of all the directions of illumination, that from below eye level, and especially from directly ahead (as oncoming traffic's headlights are), is the least effective. Why do you think that football stadiums are floodlit from high towers and not from knee level? Aside from the fact that fixed lighting from grid power is more efficient than car headlights (in the sense of lumens per energy input) where the traffic is continuous, as in towns.
As for obstrucions appearing "as a shadow" - that's bang on; it is how street lighting at one time worked by design. Sodium lighting was of a wavelength that was relected by "black" asphalt and roadside masonry, so the background was actually quite a bright yellow. Unlit objects, which generally reflected sodium light less than the road, then appeared clearly as black shapes against that background. Vehicles, in turn, formed a dark foil for their own side lights (ie running lights, not headlights).
Given that, in the UK headlights were once only used on country roads where there were no street lights. I remember driving back then in London and could even see cats or dogs crossing the road at night 800 yards ahead. Anyone with headlights on (perhaps after coming from an unlit road) would be angrily flashed at. That "system" was destroyed however in the UK by a period of patchy electrical power cuts when drivers just left their headlights on rather than bother to turn themon and off as they went in and out of lit areas. Not using headlights all the time became frowned on, and now there is no chance of seeing a pedestrian crossing the road from the opposite side behind a barrage on oncoming headlights, until they walk into your headlight beam right in front of you.