Monday, November 21, 2011

While Charging Only

Electric vehicle charging stations are being installed all around the world. For most regions this is a new experience. Many things should be considered: Where should they be installed? What are the considerations for disabled EV drivers? How should they be labeled? Many lessons will be learned over the next few years. Regardless of planning, some learnings will only happen by trial and error.

You can see in image 1 below, currently there are many ways under trial to indicate an EV parking spot.

Image 1 - The Signs of Our Time 
At some point we'll need to converge on a standard sign. Let's look at some of the aspects of EV signage. Let's start with the No Parking "circle slash P" sign that is currently used in the city of Portland.
Image 2 - Portland EV parking sign
No Parking (except electric vehicles)
To label a parking spot as "no parking" is confusing. Although confusing, since most vehicles on the road today are gas powered, this works well to ward them off from the precious few spots that currently have charging stations. As more EV parking spaces are added, I am not sure labeling them 'no parking' is the right solution. I prefer the positive expression of what can park there, rather than what can't.

For comparison, when a table is being held at a restaurant, it is not marked "no sitting, except for the party that reserved this table." While I understand, and appreciate, the 'no parking' aspect, these signs seem like they are telling a long winded story.

The lower half of this sign reads Electric Vehicle Parking Only. This should be enough to let someone know they can not park their gas car there.

Let's look at another sign.

EV Parking Only
Image 3 - Electric Car Parking
Labeling a spot ELECTRIC CAR only, as in the image above, has multiple problems. Yes CAR is fewer letters to pay the painter, but there are electric trucks and other vehicles too. My first EV was a Chevy S10 Electric; does this label mean I cannot park my truck there? Of course not. I am nit-picking; however, if this word requires me to know when I can make exceptions, then maybe other aspects of the sign are also up to drivers' interpretations. "VEHICLE" or (if you want to minimize letters) "AUTO" are better choices.

The more important part of these words is ELECTRIC. For pure electric vehicles, such as the Nissan Leaf, there is no question if they can park there, but what about vehicles like the Chevy Volt? It has had an identity crisis, with GM calling it "more car than electric", while others call it a plug-in hybrid. It has an onboard internal combustion engine that usually doesn't, but when needed can, directly provide power to the wheels. The Volt's marketing issues aside, what about Plug-in Hybrid Electric Vehicles (PHEVs) such as the Plug-in Prius? They make no claim to be electrically-only driven. Can they park there? Of course they can, they are plug-in cars.
Image 4 - Hybrid and EV ParkingImage 5 - Alt-Fuel Parking
If ELECTRIC can be interpreted to mean partially-electric as in the case of the Volt and the Plug-in Prius, then can an HEV that does not plug in, such as a Honda Civic Hybrid or a Ford Escape Hybrid, park there? Many of the alt-fuel parking signs, such as Images 4 and 5, allow HEV, biodiesel, CNG, vege oil, or H2 combustion vehicles to park there, so it is not unreasonable for HEV drivers to assume they can park in a spot like the one shown in Image 3.

What kind of vehicle is the parking spot in Image 3 really intended for? If this spot has a charging station, and the point is to make it available for plug-in cars vehicles, then this needs to be clear. Rather than referring to the vehicle's drive-train (PHEV, BEV, HEV, EREV...), what matters is whether or not it can use grid power for propulsion. Given this, the better term is PLUG-IN rather than ELECTRIC. With all of these considerations, the text for Image 3, IMHO, should read PLUG-IN VEHICLE PARKING.

One additional clarification, note that I said "use grid power for propulsion", rather than "plugs in". Plugs in could refer to a block heater or an alternator disconnect 12V battery system. Neither of these use electricity to propel the car and so should not be able to park in this spot. This is the sort of clarification that can be spelled out in local parking ordinances.

While Charging Only
Image 6 - EV parking sign in Beaverton Oregon at the Farmers Market parking lot
Another bit of text occasionally found on charging signs can be seen at the bottom of Image 6. The phrase is "While Charging" or "While Charging Only". This seems well-intentioned; once you are done charging, you should move your car and allow someone else to charge up. However, requiring the vehicle to be charging has some unintended side-effects:
  1. If someone comes along and unplugs my car, then I am suddenly illegally parked. 
  2. It prevents a charging station from servicing more than one parking spot.
  3. If my batteries fill up and stop charging, I am again, illegally parked. 
  4. Once full, if I unplug and move my car, then I can not use the remote cabin preconditioning feature without reducing my range.  
Looking at each of these carefully, you'll see that the three little words "While Charging Only" causes several problems.

The second item on this list is the one I find most troubling. If placed correctly, a single charging station can service up to six parking spots, regardless of which ones are marked EV-only. EV drivers have developed a charging station sharing protocol. This protocol lets you know when another vehicle has enough juice so you can unplug it and plug in your own vehicle. However, if the spot they are parked in is marked "While Charging" then unplugging that vehicle, even with permission, would cause them to be in violation of the parking sign.

Let's look at the example from Image 6 above. In this parking lot there are three level 2 charging stations. These are in front of parking spots #2, 4, and 6 on the east side of the lot. Only the parking spots directly in front of the stations are marked for EV only. However, due to the placement of the charging pedestals parking spots #1, 3, and 5 can also easily be serviced by these charging stations.

Say I were to pull into this parking lot and the EV only spots (2,4, & 6) are occupied. So I park in spot #1. I look and the car in spot #2 has a protocol card that says it can be unplugged at 3:00pm. I am in luck, it is 3:30. They have enough juice to get to their destination. I, on the other hand, need to charge. If there were no "While Charging" restriction, I would disconnect their car and plug mine in. In this scenario, both drivers get the charge they need and the charging station is more fully utilized. That is why it is there.

Unfortunately, this parking lot has the "While Charging" restriction shown in Image 6. So, I would not be able to charge there unless I were willing to illegally unplug the other car, where one or both of us could be ticketed. So I would either have to forgo charging or sit around waiting for one of the drivers to leave before I could plug in. Most people would do the former unless they desperately needed to charge.   

Since public infrastructure is currently rare, anything that can be done to maximize its use should be the law of the land. The point of the public charging infrastructure is to have it utilized. In this case the While Charging clause is preventing exactly that.

California recently had a bill (AB 475) to address public EV charging etiquette. General Motors asked for an amendment similar to those we discussed in the first half of this post. They wanted to make it clear that plug-in hybrid vehicles, like the Volt, would be able to legally park in "EV" parking spots. These changes make sense, but along with these changes, GM also added a "While Charging Only" requirement.

This did not go unnoticed by California's EV community. When this was pointed out, it seemed like it would be a simple matter to keep the PHEV clarifications and remove the While-Charging-clause. However, it was not that simple, GM showed their arrogance by ignoring their potential customers and advocates. They insisted that all the amendments remain. The state legislature listened to GM rather than their citizens. The bill passed the state legislature and now "While Charging Only" is the preferred sign text in the state.

Oregon and other regions that are rolling out infrastructure should learn from California's mistake. Here are a couple better alternatives: on Electric Avenue in Portland every parking spot has their own charging station, so there is no contention to plug in once you are parked. This removes the sharing hurdles that "While Charging" causes; however, the other issues remain. And having every parking spot with a charging station is obviously not a scalable solution. Considering the associated costs a station should be installed such that it can service as many possible parking spots as possible.

The second solution they use is simply restricted parking times. Like most street parking in downtown Portland, these Electric Avenue spots have time restrictions. The DC Quick Charger parking spot is limited to one hour. This ensures some level of turn over on this high-demand spot. Of course, putting time restrictions on level 2 spots will mean that drivers will not be able to fill up from empty, but topping up with a mid-day convenience 1-4 hour charge should be all that most drivers need. Parking garages, home charging, and DC quick charging can handle the rest.

For EV parking signage there are several semantic considerations. A sign should:
  • not say car, if vehicle is what is meant
  • not say electric vehicle, if plug-in vehicle is what is meant
Labeling a parking spot as "No Parking" only adds to confusion. I prefer "Plug-In Vehicle Only". And finally, "While Charging" should not be part of the signage. If the goal of these signs is to increase public infrastructure utilization, in practice, these words have the opposite result. In areas where there is contention for EV parking spots, simple time restrictions, like most urban parking areas already have, gives more vehicles a chance to participate and improves infrastructure utilization.


  1. I personally prefer the “no parking” signage; the Portland World Trade Center used to have green “electric vehicle parking” signs, and the number of gas cars that parked there was tremendous; every time I would go there would be a gas car parked in those spaces. I watched the City go through several iterations of signage, all with the green “P” and some version of "EVs only." The problem was, people don’t read the signs. All they saw was the green “P” and they figured they were good to go. They even tried the no parking “P” and the green parking “P” together, and that only made things more confusing. It was only once they got rid of the green “P” entirely and made it simply “no parking” that the number of violators declined, at least in my anecdotal experience. While you may dislike the “no parking” signage, it is proven effective where anything and everything else has not been, so I don’t foresee it changing anytime soon unless the MUTCD specifies a national sign.

    I dislike the idea of plug-in hybrids (PHEVs) like the Volt or Prius being explicitly allowed to use the public charging stations, because unlike pure EVs they don’t have to plug-in when the battery runs out. It may be fine for now when the number of vehicles is still relatively small, but as that number grows it’s only going to create conflict, and competition for the limited number of public chargers. For PHEVs public charging stations are a mere convenience, while for BEVs they are an absolute necessity, and as soon as Leaf or iMIEV drivers start getting stranded because a Volt or Prius driver wanted to top off, those laws that explicitly allow PHEVs are going to be reconsidered.

    As for the “parking only while charging” requirement, this needs to be implemented on a site-specific, case-by-case basis. If every parking stall has an EV charger, as on Portland’s Electric Avenue, then you have no business parking there if you aren’t plugged in. If multiple stalls are expected to share a single charger, then the requirement doesn’t make sense.

    One of the things I like about parking in downtown Portland is they you have to pay by the hour to park, which helps prompt drivers to use the chargers only when they really need to. This is in contrast to California where EVs get free parking in many places, which encourages drivers to park there all day, blocking the station whether they actually need it or not; this is why they need a charger sharing protocol. By having pay parking, it encourages quick turnaround; charge up and move on. Yes, if you re-park your car elsewhere you lose the ability to pre-condition, but if your required range is that close to the margin already, then you need to investigate a different vehicle, (because if nothing else, age-related battery degradation is eventually going to leave you stranded.) Done correctly, pay-parking eliminates the need to share a charging station, and if the cost prompts you to take the bus or ride a bike instead of paying a fortune for parking, all the better.

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