Here are two articles talking about legislation to make LED street lighting mandatory here in Nova Scotia, Canada. It doesn't mention private yard lighting, though.

http://www.gov.ns.ca/news/details.asp?id=20110421003

http://www.cbc.ca/news/canada/nova-scotia/story/2012/05/14/ns-led-lights-power.html

I guess that a new meaning for HID could be high intensity disgrace !

They are changing HPS to LED, yet HPS is more efficient. Go figure

They are, indeed. I have not seen LED luminaires here that are of a different wattage than 110 W. Most HPS are 150 W for main streets in cities, and 100 W for lesser traveled streets. Some residential streets have 70 watts, but in my area (rural), the places that have street lighting are all 100 watts. Major intersections are 250 watts.

One intersection near my home had a 180 watt SOX on an aluminium pole. Someone (or construction equipement, they were paving at the time) struck the pole, which did not suffer damage. However, the SOX fitting bounced so much that the lamp/reflector/lens assembly broke off the ballast housing and crased down. It was replaced with a cobra head of 250 watt HPS. This HPS fixture was there for about 9 months and was replaced with a 110 watt LED.

Is the lighting level generally high or low with HPS ?

If it is high, there is no way the LED can beat the HPS

If it is low, the LED is likely to be more efficient than the HPS. But then there is MH which i think is about on par with the LED in efficiency, and i wonder about lifetime

The illumination level is quite high with HPS. It seems a bit dimmer with the LED where they are already fitted.

For lifespan, I don't know yet, however some of the individual diodes (or group of diodes) in fixtures are blinking at about 1Hz. I wonder if this blinking is a sign of LED eol ?

With the theory that LEDs last a very long time, you get the efficiency of the MH, the colour of MH but not the relamping of MH. Only time will tell what is the lifespan of the new fixtures...

I hope yard lights will not be included in the legislation.

1Hz look like a driver failure (thats what i am familiar with from power supplies based on the 3845 or similar chip) but then it would affect all of the LEDs on the same driver - which is at least a continuous block in the fixture or the entire fixture

Otherwise it may be mechanical like failed soldering or failed bonding wire inside 1 LED but they are in series andthats how it extinguish a block of them. In this case it will probably behave accordingly if you hit the pole when standing on earth. The mechanical process can be repetitive due to thermal expansion opening a contact, going off, cooling down, closing contact etc but in this case it wont be exact 1Hz but probably somewhat irregular flashing, like xmas lights with thermal flashers

Any mercury street lights left in Nova Scotia? What I don't understand in the latest news article that only city owned lights are required to be changed?

Ash : They are flashing in a regular ~1Hz interval, so I suspect a driver problem too. There is about one third of the LEDs in the fixture that flash, the rest light up normally.

Silverliner : There are still a few MV street lights left in Nova Scotia. As far as I know, they are still relamped as necessary. There are two types of street lighting here : power company owned and maintained, and city owned (not sure who maintains city lighting - could be the power company through a contract). It is my understanding that the city owned lighting is the problem because of the cost to taxpayers. The utility owned lights will, however, be changed as well, but the people have not yet started complaining about the cost. There are other problems with the management of the utility (which is a privately owned company) where the top management get significant salary raises and bonuses, while increasing the energy rate...

As for rented area lights, there are still a few mercury ones left, the majority being HPS. This is an example of a MV area light rented by a store. It now has a new photocell, as well as a new lamp. This was done in the summer of 2011, much to my surprise. I have seen other cases where wooden power poles were replaced, and the mercury vapour fixture was reinstalled on the new pole (in the last year).

My biggest fear of this legislation is that they would force homeowners to change privately owned and maintained mercury fixtures.

Do they have the right to ? It is you who is paying the electricity for your lights

in my city they replaced some 400w mh with leds.

less luminous (but i don't know leds wattage)
some leds failed before an year of operation (you can see black lines in the fixtures).

i think leds can be an good solution (with proper optical control), but driver must be simple and reiable: i experimented new chips (smd hell) and they aren't reiable (some failed after 1/2 hour).

now i'm testing an homemade driver with ne555, and it seems reiable due semplicity.

Typical problems come down to this :

Bad electrolytic capacitors

Bad AC capacitor in "voltage divider" which extracts low voltage from line voltage without transformer

Condensation on the circuit or on the fixture's inner surface then dripping into the components

Breaking solderings from repeated thermal expansion and contraction

LEDs failing from electromigration when used at too high current (actually even their rated 20mA is too high)

ash, 20mA is too low for power leds

I mean for ordinary 5mm LEDs in huge clusters like some of the fixtures are made. Better not go with them above 10mA

Power LEDs have the problem to a lower extent as they at least have a place to attach heatsink. But the heatsink size and amount of power dissipated into it (from multiple LEDs) still is often insufficient so better to not use the LEDs at their max rating

Typical problems come down to this :

Bad electrolytic capacitors

Ash: You said me yourself that the LED driver don't contains an electrolytic capacitor: The reason why LED lamps, even the cheapest ones, are compatible with incandescent dimmers.

Some do have them, and some dont

Streetlights and generally larger clusters of LEDs sometimes use a switching power supply control, where the control itself is powered by DC and stabilized with the use of electrolitic capacitor

One reason is that this allows them to be dimmed (by the control) with the use of more advanced systems like DALI and X10. The dimming is not done by switching the electrical line itself like done by a dimmer switch at home. So the capacitor-less dimmable LED circuits for home use won't work there. The more fancy electronic control will but it requires a capacitor

Another reason is that some circuits may be required to have PFC - power factor correction, to get the power factor up (as it can be as low as 0.5 in some electronic ballasts, overloding the lines). Passive PFC is basically an inductor in series with the circuit. Think of it as magnetic ballast, from the output of which the electronic ballast is powered. But it does not get power factor of 1. Active PFC is an electronic addition that can get really good power factors of about 0.99, but it requires an elecronic control and this again may include electrolitic capacitors