Greenhouse in eternal light

My greenhouse is also under railway lights and I've never noticed any ill effects to seed germination or plants growing in there.

I believe its also about the colour of the light, mercury vapour and metal halide lamps were designed to hit a certain bandwidth, I think street lamps will have little effect.

I've wonder the same about my indoor chilli plants. They are under grow lights that go off in the evening but I still have lamps on until I go to bed.

I think given the strength of the artificial light from my lamps that reaches the plants is about 50 Lux in (measurement of light intensity), the fact this is so much less than daylight levels means the plants aren't fooled into thinking it's still daytime.

Here's some data I pinched from Wikipedia on relative light levels:

120,000 lux Brightest sunlight
111,000 lux Bright sunlight
20,000 lux Shade illuminated by entire clear blue sky, midday
1,000 - 2,000 lux Typical overcast day, midday
<200 lux Extreme of darkest storm clouds, midday
400 lux Sunrise or sunset on a clear day (ambient illumination).
40 lux Fully overcast, sunset/sunrise
<1 lux Extreme of darkest storm clouds, sunset/rise

So my evening lighting at 50 Lux is right at the bottom of the scale. You could try measuring the light level, which could put your mind at rest... If you have a smartphone you might be able to use an app to test the light level, I use one on my Android phone called Light Meter, it seems actually very accurate.

Artificial lighting is very deceptive, our eyes don't perceive it as being many hundred of times dimmer than sunlight.

If you do notice slowed growth could you put a barrier on one side of the greenhouse etc. to block the street lighting but not too much sunlight? I do reckon it's unlikely the light levels will require it though.