HOV Access Is Key For California Plug-in Car Purchases

A UC Davis study published in April showed that a good third to almost 60 percent of California plug-in vehicle (PEV) purchases are primarily motivated by solo access to high occupancy vehicle (HOV) lanes – which can become congested at times.

California is the leader in PEV acceptance, and policymakers adopting a carrot-and-stick approach of incentives and perks have long included stickers that give alternative-energy car buyers access to (usually) less congested lanes.

Last decade yellow stickers were adopted for hybrid vehicle applicants, and more recently, there have been green stickers for transitional zero emission vehicles (TZEV) and white for Federal Inherently Low Emission Vehicles (ILEVs).

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Researchers at the UC Davis Institute of Transportation Studies interviewed more than 3,500 California PEV owners in coordination with the California Center for Sustainable Energy administering the survey on behalf of the California Air Resources Board.

Out of 3,500 PEV owners or lessors, 3,000 said they applied for and received a green or white decal, and 500 did not.

The percentage of those who applied include 95 percent Prius plug-in hybrid, 89 percent Chevy Volts, and 79 percent Nissan Leafs.

“When asked about their primary motivation to buy the car,” wrote authors Gil Tal and Michael Nicholas, “57% of Plug-in Priuses, 34% of Volts and 38% of Leafs identified it as the HOV decal (a more recent 4Q 2013 analysis shows somewhat lower percentages – 34%, 20%, and 15% respectively.”

"As expected the motivation in the Los Angeles region and the Bay Area, areas with high benefit of using decals, is higher than other regions," wrote the authors. "We also notice that in the Los Angeles region, an area with longer average trips, the impact on the Plug-In Prius is higher than on other vehicle types. More than 80% of the PEVs are being used for commuting which is highly correlated with applying for decals though only 58% commute with this car daily. Leaf drivers and “other” car drivers which are mostly BEVs have a lower commute frequency than PHEV drivers."

“As expected the motivation in the Los Angeles region and the Bay Area, areas with high benefit of using decals, is higher than other regions,” wrote the authors. “We also notice that in the Los Angeles region, an area with longer average trips, the impact on the Plug-In Prius is higher than on other vehicle types. More than 80% of the PEVs are being used for commuting which is highly correlated with applying for decals though only 58% commute with this car daily. Leaf drivers and ‘other’ car drivers which are mostly BEVs have a lower commute frequency than PHEV drivers.”

Among other key findings, the authors discovered HOV access as the main purchase motivation is higher in the more densely congested Bay Area and Los Angeles than in other regions. These areas generally have more congestion on freeway and more HOV lanes available.

The study confirmed also more than 80 percent of PEVs are being used for commuting, and BEVs have a lower commute frequency than PHEV drivers.

Also, the study shows a higher frequency of Prius plug-in owners which reduces the number of electric miles in the HOV lane.

"We observe in Figure 2 significantly higher household income of owners with HOV access decals comparing to owners without decals ($173,000 with a decal vs. $145,000 without a decal)." said the authors. "Since different areas have different median incomes and HOV lanes are more likely to be in higher income regions, the income spread is also useful to examine."

“We observe in Figure 2 significantly higher household income of owners with HOV access decals comparing to owners without decals ($173,000 with a decal vs. $145,000 without a decal).” said the authors. “Since different areas have different median incomes and HOV lanes are more likely to be in higher income regions, the income spread is also useful to examine.”

The study further found higher income earners were more likely to take advantage of the HOV sticker perk. It is believed one reason is time is money to them, so saving minutes on busy freeways is a motivator.

In all, “the impact of the HOV decals as well as the state rebate is different for each household based on the location, travel needs, income and other socio economic variables,” said the authors.

It’s being postulated that the effectiveness of this benefit could be increased by prioritizing PHEVs with larger all-electric range and not to just any PHEV, particularly those with a short range such as the Prius rated at around 11 miles more or less.


"The amount of zero emission usage of both BEVs and PHEVs can be measured in electric vehicle miles traveled or eVMT while the incentive performance of the HOV decals can be measured in terms of eVMT per mile of HOV usage," said the authors. "As expected, users with decals drive more and create more eVMT than those without decals except from Plug-in Prius drivers who show no significant change (Figure 3)."

“The amount of zero emission usage of both BEVs and PHEVs can be measured in electric vehicle miles traveled or eVMT while the incentive performance of the HOV decals can be measured in terms of eVMT per mile of HOV usage,” said the authors. “As expected, users with decals drive more and create more eVMT than those without decals except from Plug-in Prius drivers who show no significant change (Figure 3).”

“Smaller battery PHEVs are more likely to be purchased because of the HOV decal incentive but have fewer electric miles,” said the authors. “Differentiating decal access between the PHEVs based on their electric range will maximize eVMT (electric vehicle miles traveled). This can be done by raising the minimum battery size requirement, creating a separate quota for each PHEV type or by creating a different sunset date for each vehicle type.”

The California green sticker for PHEVs did reach a 40,000 sticker maximum threshold in May. The California Air Resources Board extended this on July 1, 2014 by 15,000 more green stickers through Jan. 1, 2019.

There is no cap on the white stickers, and this program also will run through Jan. 1, 2019.

As for the earlier yellow stickers for regular hybrids, these are no longer valid, and the program ended July 2011 as the new wave of plug-in cars were just getting started.

Source: UC Davis