The Strange Case of the Killer Therac-25

Killed By A Machine: The Therac-25


The Therac-25 went into service in 1983. For several years and thousands of patients there were no problems. On June 3, 1985, a woman was being treated for breast cancer. She had been prescribed 200 Radiation Absorbed Dose (rad) in the form of a 10 MeV electron beam. The patient felt a tremendous heat when the machine powered up. It wasn’t known at the time, but she had been burned by somewhere between 10,000 and 20,000 rad. The patient lived, but lost her left breast and the use of her left arm due to the radiation.

On July 26, a second patient was burned at The Ontario Cancer Foundation in Hamilton, Ontario, Canada. This patient died in November of that year. Autopsy ruled that the death was due to a particularly aggressive cervical cancer. Had she lived however, she would have needed a complete hip replacement to correct the damage caused by the Therac-25.

In December of 1985, a third woman was burned by a Therac-25 installed in Yakima, Washington. She developed a striped burn pattern on her hip which closely matched the beam blocking strips on the Therac-25. This patient lived, but eventually needed skin grafts to close the wounds caused by radiation burns.

On March 21, 1986, a patient in Tyler, Texas was scheduled to receive his 9th Therac-25 treatment. He was prescribed 180 rads to a small tumor on his back. When the machine turned on, he felt heat and pain, which was unexpected as radiation therapy is usually a painless process. The Therac-25 itself also started buzzing in an unusual way. The patient began to get up off the treatment table when he was hit by a second pulse of radiation. This time he did get up and began banging on the door for help. He received a massive overdose. He was hospitalized for radiation sickness, and died 5 months later.

On April 11th, 1986, a second accident occurred in Tyler, Texas. This time the patient was being treated for skin cancer on his ear. The same operator was running the machine as in the March 21st accident. When therapy started, the patient saw a bright light, and heard eggs frying. He said it felt like his face was on fire. The patient died three weeks later due to radiation burns on the right temporal lobe of his brain and brain stem.

The final overdose occurred much later, this time at Yakima Valley hospital in January, 1987. This patient later died due to his injuries.

After each incident, the local hospital physicist would call AECL and the medical regulation bureau in their respective countries. At first AECL denied that the Therac-25 was capable of delivering an overdose of radiation. The machine had so many safeguards in place that it frequently threw error codes and paused treatment, giving less than the prescribed amount of radiation. After the Ontario incident, it was clear that something was wrong. The only way that kind of overdose could be delivered is if the turntable was in the wrong position. If the scanning magnets or X-ray target were not in position, the patient would be hit with a laser-like beam of radiation.

AECL carefully ran test after test and could not reproduce the error. The only possible cause they could come up with was a temporary failure in the three microswitches which determined the turntable’s position. The microswitch circuit was re-designed such that the failure of any one microswitch could be detected by the computer. This modification was quickly added and was in place for the rest of the accidents.

If this story has a hero, it’s [Fritz Hager], the staff physicist at the East Texas Cancer Center in Tyler, Texas. After the second incident at his facility, he was determined to get to the bottom of the problem. In both cases, the Therac-25 displayed a “Malfunction 54” message. The message was not mentioned in the manuals. AECL explained that Malfunction 54 meant that the Therac-25’s computer could not determine if there a underdose OR overdose of radiation.

The same radiotherapy technician had been involved in both incidents, so [Fritz] brought her back into the control room to attempt to recreate the problem. The two “locked the doors” NASA style, working into the night and through the weekend trying to reproduce the problem. With the technician running the machine, the two were able to pinpoint the issue. The VT-100 console used to enter Therac-25 prescriptions allowed cursor movement via cursor up and down keys. If the user selected X-ray mode, the machine would begin setting up the machine for high-powered X-rays. This process took about 8 seconds. If the user switched to Electron mode within those 8 seconds, the turntable would not switch over to the correct position, leaving the turntable in an unknown state.

It’s important to note that all the testing to this date had been performed slowly and carefully, as one would expect. Due to the nature of this bug, that sort of testing would never have identified the culprit. It took someone who was familiar with the machine – who worked with the data entry system every day, before the error was found. [Fritz] practiced, and was eventually able to produce Malfunction-54 himself at will. Even with this smoking gun, it took several phone calls and faxes of detailed instructions before AECL was able to obtain the same behavior on their lab machine. [Frank Borger], staff physicist for a cancer center in Chicago proved that the bug also existed in the Therac-20’s software. By performing [Fritz’s] procedure on his older machine, he received similar error, and a fuse in the machine would blow. The fuse was part of a hardware interlock which had been removed in the Therac-25.

As the investigations and lawsuits progressed, the software for the Therac-25 was placed under scrutiny. The Therac-25’s PDP-11 was programmed completely in assembly language. Not only the application, but the underlying executive, which took the place of an operating system. The computer was tasked with handling real-time control of the machine, both its normal operation and safety systems. Today this sort of job could be handled by a microcontroller or two, with a PC running a GUI front end.

AECL never publicly released the source code, but several experts including [Nancy Leveson] did obtain access for the investigation. What they found was shocking. The software appeared to have been written by a programmer with little experience coding for real-time systems. There were few comments, and no proof that any timing analysis had been performed. According to AECL, a single programmer had written the software based upon the Therac-6 and 20 code. However, this programmer no longer worked for the company, and could not be found.
Comment: Good Wiki article


Cancer "Whac-A-Mole" - Answering a friend: "What stage is your prostate cancer?"

In terms the juvenile Jim Peet best understands ... we are playing "whac-a-mole" with the cancer ... beating it down whenever and wherever it pops up!


What's External Beam Radiotherapy (EBRT) like?

  • It's distantly like James Bond in Goldfinger
  • There is a monstrously large machine
  • I'm reclined on a table
  • My legs are spread
  • I'm restrained
  • And a laser is creeping steadily towards my gonads
  • I say, "Do you expect me to talk?"
  • And the radiation tech says: "No, Mr. Peet, I expect you to die!"
  • It's very scary
Scratch that!
  • There is a table
  • There is a monstrously large machine
  • I am reclined (but not restrained)
  • It does target my groin area
  • It's not scary!
Here's how it works:

  • I go daily to the Park Nicollet Frauenshuh Cancer Center in Saint Louis Park
  • There is a special entrance with a small parking lot here
  • I am ⅓ way through 39 treatments
  • The machine is a Varian Truebeam (image below)
  • At my appointed hour ...
  • I am helped onto a horizontal bed by two radiation techs
  • I lower my slacks and undies ... a towel is over my private parts
  • I am carefully positioned via laser that triangulates on three small tattoos
  • The radiation techs exit the room and a very large 18" thick door glides closed
  • The machine does a quick CAT scan to precisely target the radiation
  • A large round irradiator passes over me twice
  • The machine resets
  • The thick door opens and the techs return
  • I'm helped off the bed
  • I dress and am done

The Therac-25 - an important object lesson on QA testing

Me with Radiation Tech before Varian Truebeam

My schedule


Reactions to Trump Recognizing Jerusalem as Israel's Capital Echo Truman's Decision to Recognize Israel

U.S. to Recognize Jerusalem as Israel’s Capital, Trump Says, Alarming Middle East Leaders


President Trump told Israeli and Arab leaders on Tuesday that he plans to recognize Jerusalem as the capital of Israel, a symbolically fraught move that would upend decades of American policy and upset efforts to broker peace between Israel and the Palestinians.

Mr. Trump is expected to announce his decision on Wednesday, two days after the expiration of a deadline for him to decide whether to keep the American Embassy in Tel Aviv.

Palestinian officials said Mr. Trump told the president of the Palestinian Authority, Mahmoud Abbas, that the United States would move the embassy to Jerusalem. Jordan said the president gave a similar message to King Abdullah II.

American officials, however, said such a move could not occur immediately for logistical reasons, given the lack of facilities to house the embassy staff. As a result, Mr. Trump is expected to sign a national security waiver that would authorize the administration to keep it in Tel Aviv for an additional six months.

Still, Mr. Trump’s decision to recognize Jerusalem as the capital — and to set in motion an embassy move — is his riskiest foray yet into the thicket of Middle East diplomacy. Arab and European leaders warn that it could derail any peace initiative and even ignite fresh violence in the region.

Other headlines

Go back to May 14th, 1948

The reactions from "The Wise Men"

The President regarded his Secretary of State, General of the Army George C. Marshall, as “the greatest living American.” Yet the two men were on a collision course over Mideast policy, which, if not resolved, threatened to split and wreck the Administration. British control of Palestine would run out in two days, and when it did, the Jewish Agency intended to announce the creation of a new state, still unnamed, in part of Palestine.

Marshall firmly opposed American recognition of the new Jewish state; I did not. Marshall’s opposition was shared by almost every member of the brilliant and now-legendary group of men, later referred to as “the Wise Men,” who were then in the process of creating a postwar foreign policy that would endure for more than forty years. The opposition in­cluded the respected Undersecretary of State, Robert Lovett; his prede­cessor, Dean Acheson; the number-three man in the State Department, Charles Bohlen; the brilliant chief of the Policy Planning Staff, George F. Kennan; the dynamic and driven Secretary of Defense, James V. Forrestal; and a man with whom I would disagree again twenty years later when we served together in the Cabinet, Dean Rusk, then the Director of the Office of United Nations Affairs.

Some months earlier, during one of our weekly breakfasts at his ele­gant Georgetown home, Forrestal had spoken emotionally and frankly to me concerning his opposition to helping the Zionists, as advocates of the creation of a Jewish state were called. “You fellows over at the White House are just not facing up to the realities in the Middle East. There are thirty million Arabs on one side and about six hundred thousand Jews on the other. It is clear that in any contest, the Arabs are going to overwhelm the Jews. Why don’t you face up to the realities? Just look at the numbers!” 

“Jim, the President knows just as well as you do what the numbers are,” I replied, “but he doesn’t consider this to be a question of numbers. He has always supported the right of the Jews to have their own homeland, from the moment he became President. He considers this to be a question about the moral and ethical considerations that are present in that part of the world. For that reason, he supports the foundation of a Jewish state. He is sympathetic to their needs and their desires, and I assure you he is going to continue to lend our country’s support to the creation of a Jewish state.”

Forrestal answered bluntly: “Well, if he does that, then he’s absolutely dead wrong.” His attitude was typical of the foreign policy establishment, especially the pro-Arab professionals at the State Department, who, deeply influenced by the huge oil reserves in the Mideast, supported the side they thought would be the likely winner in the struggle between the Arabs and the Jews. Officials in the State Department had done every­thing in their power to prevent, thwart, or delay the President’s Palestine policy in 1947 and 1948, while I fought for assistance to the Jewish Agency. Watching them find various ways to avoid carrying out White House instructions, I sometimes felt, almost bitterly, that they preferred to follow the views of the British Foreign Office rather than those of their President.

At midnight on May 14, 1948 – 6 p.m. in Washington – the British would relinquish control of Palestine, which they had been administering since World War I under mandate from the League of Nations. One minute later, the Jewish Agency, under the leadership of David Ben­-Gurion, would proclaim the new state. (The name “Israel” was as yet unknown, and most of us assumed the new nation would be called “Ju­daea.”) The neighboring Arabs made it clear that the fighting, which had already begun, would erupt into a full-scale war against the new state the moment the British left. In order to avoid this, the British and the State Department wanted to turn Palestine over to the trusteeship of the United Nations – a position I strongly opposed as dangerous to the sur­vival of the beleaguered Jews in Palestine. I already had had several serious disagreements over State’s position with General Marshall’s protégé, Dean Rusk, and with Loy Henderson, the Director of Near Eastern and African Affairs. Henderson, a mustachioed, balding, tightly controlled and somewhat pompous career diplomat, was strongly pro-Arab and heav­ily influenced by the British. I had no firsthand evidence of it, but I knew Henderson was among a group of Mideast experts in the State Depart­ment who were widely regarded as anti-Semitic. He had no use for White House interference in what he regarded as his personal domain – Ameri­can policy in the Mideast.

On May 7, a week before the end of the British Mandate, I met with President Truman for our customary private day-end chat in the Oval Office. In these informal sessions, which were never listed on his official schedule, he was often very blunt. No one else knew what passed between us in those sessions unless he wanted them to. In this case he didn’t.

I handed him a draft of a public statement I had prepared, and pro­posed that at his next press conference – scheduled for May 13, the day before the British Mandate would end – he announce his intention to recognize the Jewish state. The President was sympathetic to the pro­posal; keenly aware of Secretary Marshall’s strong feelings, though, he picked up the telephone to get his views. As I sat listening to the Presi­dent’s end of the conversation, I could tell that Marshall objected strongly to the proposed statement. The President listened politely, then told Marshall he wanted to have a meeting on the subject. 

I was sitting, as usual, in a straight-backed chair to the left of the President’s desk. As he ended the conversation with Marshall, he swiveled his chair back toward me. “Clark, I am impressed with General Marshall’s argument that we should not recognize the new state so fast,” he said. “He does not want to recognize it at all, at least not now. I’ve asked him and Lovett to come in next week to discuss this business. I think Marshall is going to continue to take a very strong position. When he does, I would like you to make the case in favor of recognition of the new state.” He paused, then looked at me intently for a moment. “You know how I feel. I want you to present it just as though you were making an argument before the Supreme Court of the United States. Consider it carefully, Clark, organize it logically. I want you to be as persuasive as you possibly can be.”

At 4 p.m. on Wednesday, May 12, a cloudless, sweltering day, we assembled in the Oval Office. President Truman sat at his desk, his back to the bay window overlooking the lawn, his famous THE BUCK STOPS HERE plaque in front of him on his desk. In the seat to the President’s left sat Marshall, austere and grim, and next to Marshall sat his deputy, Robert Lovett. Behind Lovett were two State Department officials, Robert McClintock and Fraser Wilkins. I wondered why Rusk and Henderson, who had been centrally involved in every phase of the policy debate for months, were not present. Only forty years later did I learn from Wilkins that just before the meeting Lovett had decided the presence of Rusk and Henderson in the same room with me would be too inflammatory, and he had substituted their deputies.

David Niles, White House Appointments Secretary Matthew Con­nelly, and I sat together in chairs to the right of the President. As the meeting began, exactly fifty hours remained before the new nation, still without a name, would be born.

The meeting began in a deceptively calm manner. President Truman did not raise the issue of recognition; he wanted me to raise it, but only after Marshall and Lovett had spoken, so he would be able to ascertain the degree of Marshall’s opposition before showing his own hand. Lovett began by criticizing what he termed signs of growing “assertiveness” by the Jewish Agency. “On the basis of some recent military successes and the prospect of a ‘behind the barn’ deal with King Abdullah,” Lovett said, “the Jews seem confident that they can establish their sovereign state without any necessity for a truce with the Arabs of Palestine.”

Marshall interrupted Lovett: he was strongly opposed, he said, to the behavior of the Jewish Agency. He had met on May 8 with Moshe Shertok, its political representative, and had told him that it was “danger­ous to base long-range policy on temporary military success.” Moreover, if the Jews got into trouble and “came running to us for help,” Marshall said he had told them, “they were clearly on notice that there was no warrant to expect help from the United States, which had warned them of the grave risk they were running.” I was surprised to hear, from Marshall himself, how bluntly he had dealt with Shertok. He had laid down a tough opening position.

As Marshall spoke, he was interrupted by an urgent message from his special assistant. The United Press had reported that Shertok had re­turned to Tel Aviv carrying Marshall’s personal warning to David Ben-Gurion. Clearly displeased, Marshall told us that not only had he not sent Ben-Gurion a message, but he had never even heard of Ben-Gurion – a surprising statement about the leader of the Jewish Agency, who was about to become the new nation’s Prime Minister.

Marshall directed the State Department to refuse to comment on the UP news story, and then concluded his presentation. The United States, he said, should continue supporting UN trusteeship resolutions and defer any decision on recognition.

It was now my turn. Even though I disagreed with many of Marshall’s and Lovett’s statements, I had waited without saying a word until the President called on me – in order to establish that I was speaking at his request, not on my own initiative.

I began by objecting strongly to the State Department’s position paper reaffirming American support of Security Council efforts to secure a truce in Palestine. “There has been no truce in Palestine and there almost certainly will not be one,” I said. I reminded everyone that in a meeting chaired by the President on March 24, “Dean Rusk stated that a truce could be negotiated within two weeks. But this goal is still not in sight.”

“Second,” I went on, “trusteeship, which State supports, presupposes a single Palestine. That is also unrealistic. Partition into Jewish and Arab sectors has already happened. Jews and Arabs are already fighting each other from territory each side presently controls.”

The time had now come to join the issue. “Third, Mr. President,” I said, “I strongly urge you to give prompt recognition to the Jewish state immediately after the termination of the British Mandate on May 14. This would have the distinct value of restoring the President’s firm posi­tion in support of the partition of Palestine. Such a move should be taken quickly, before the Soviet Union or any other nation recognizes the Jewish state.”

I knew my comment would displease Marshall and Lovett, since I was implying that State had embarrassed the President by reversing the Amer­ican position in the UN two months earlier. But I strongly believed this, and I saw no reason not to bring it up.

“My fourth point,” I continued, “is that the President should make a statement at his press conference tomorrow which announces his inten­tion to recognize the Jewish state, once it has complied with the provision for democratic government outlined in the UN resolution of November 29, [1947]. I understand this is in fact the case, and therefore presents no prob­lem.” I handed around the room a proposed press statement, and read aloud its conclusion: “I have asked the Secretary of State to have the Representatives of the United States in the United Nations take up this subject with a view toward obtaining early recognition of the Jewish state by the other members of the United Nations.” When everyone had examined it, I went on, “My fifth point relates to the Balfour Declaration. Jewish people the world over have been waiting for thirty years for the promise of a homeland to be fulfilled. There is no reason to wait one day longer. Trusteeship will postpone that promise indefinitely. Sixth, the United States has a great moral obligation to oppose discrimination such as that inflicted on the Jewish people. Alarmingly, it is reappearing in communist-controlled Eastern Europe. There must be a safe haven for these people. Here is an opportunity to try to bring these ancient injustices to an end. The Jews could have their own homeland. They could be lifted to the status of other peoples who have their own country. And perhaps these steps would help atone, in some small way, for the atrocities, so vast as to stupefy the human mind, that occurred during the Holocaust.”

“Finally,” I concluded, “I fully understand and agree that vital national interests are involved. In an area as unstable as the Middle East, where there is not now and never has been any tradition of democratic govern­ment, it is important for the long-range security of our country, and indeed the world, that a nation committed to the democratic system be established there, one on which we can rely. The new Jewish state can be such a place. We should strengthen it in its infancy by prompt recognition.”

I had noticed Marshall’s face reddening with suppressed anger as I talked. When I finished, he exploded: “Mr. President, I thought this meeting was called to consider an important and complicated problem in foreign policy. I don’t even know why Clifford is here. He is a domestic adviser, and this is a foreign policy matter.”

President Truman with Clack Clifford
I would never forget President Truman’s characteristically simple reply: “Well, General, he’s here because I asked him to be here.”

Marshall, scarcely concealing his ire, shot back, “These considerations have nothing to do with the issue. I fear that the only reason Clifford is here is that he is pressing a political consideration with regard to this issue. I don’t think politics should play any part in this.”

Lovett joined the attack: “It would be highly injurious to the United Nations to announce the recognition of the Jewish state even before it had come into existence and while the General Assembly is still considering the question. Furthermore, such a move would be injurious to the prestige of the President. It is obviously designed to win the Jewish vote, but in my opinion, it would lose more votes than it would gain.” Lovett had finally brought to the surface the root cause of Marshall’s fury – his view that the position I presented was dictated by domestic political considera­tions, specifically a quest for Jewish votes.

“Mr. President, to recognize the Jewish state prematurely would be buying a pig in a poke,” Lovett continued. “How do we know what kind of Jewish state will be set up? We have many reports from British and American intelligence agents that Soviets are sending Jews and commu­nist agents into Palestine from the Black Sea area.” Lovett read some of these intelligence reports to the group. I found them ridiculous, and no evidence ever turned up to support them; in fact, Jews were fleeing communism throughout Eastern Europe at that very moment.

When Lovett concluded, Marshall spoke again. He was still furious. Speaking with barely contained rage and more than a hint of self-righ­teousness, he made the most remarkable threat I ever heard anyone make directly to a President: “If you follow Clifford’s advice and if I were to vote in the election, I would vote against you.” (Emphasis added.)

Everyone in the room was stunned. Here was the indispensable symbol of continuity whom President Truman revered and needed, making a threat that, if it became public, could virtually seal the dissolution of the Truman Administration and send the Western Alliance, then in the process of creation, into disarray before it had been fully structured. Marshall’s statement fell short of an explicit threat to resign, but it came very close.

Lovett and I tried to step into the ensuing silence with words of conciliation. We both knew how important it was to get this dreadful meeting over with quickly, before Marshall said something even more irretrievable. My suggested Presidential press statement was clearly out of the question, and I withdrew it. Lovett said that State’s Legal Adviser, Ernest Gross, had prepared a paper on the legal aspects of recognition, and he would send it to us immediately.

President Truman also knew he had to end the meeting. He said he was fully aware of the dangers in the situation, to say nothing of the political factors involved on both sides of the problem; these were his responsibility, and he would deal with them himself. Seeing Marshall was still very agitated, he rose and turned to him and said, “I understand your position, General, and I’m inclined to side with you in this matter.”

We rose with the President and gathered our papers. Marshall did not even glance at me as he and Lovett left. In fact, not only did he never speak to me again after that meeting, but, according to his official biogra­pher, he never again mentioned my name.




The CVS Aetna merger

CVS is buying Aetna for $69 billion


Pharmacy chain CVS Health (CVS) is acquiring health insurance giant Aetna (AET) in a $69 billion deal that could reshape American health care.

“This combination brings together the expertise of two great companies to remake the consumer health care experience,”CVS CEO Larry Merlo said. “With the analytics of Aetna and CVS Health’s human touch, we will create a health care platform built around individuals.”

“Together with CVS Health, we will better understand our members’ health goals, guide them through the health care system and help them achieve their best health,” Aetna CEO Mark Bertolini said.

Aetna shareholders will receive approximately $207 per share, $145 per share in cash and 0.8378 CVS shares for each share of Aetna.

Comment: We have both in an IRA


Bull Market Apogee Predicted - 2,863

Bank of America sees end of bull market coming in 2018


Here's how it will happen:
  • Bank of America Merrill Lynch predicts "capitulation" for the bull market in 2018, with the S&P 500 peaking at 2,863.
  • Strategist Michael Hartnett said the firm is prepared to "downgrade risk aggressively" once it sees the triggers in place.
  • A shift from passive to active in investor allocations would be one of the signs that the rally is about over.

Comment: Sounds plausible. 2,863 is 10% above today's level. Chart top is from the data below.

   Milestone     Date Achieved 
1,805 11/22/13
1,901 5/23/14
2,000 8/26/14
2,100 2/17/15
2,203 11/22/16
2,308 2/9/17
2,402 5/15/17
2,500 9/15/17
2,594 11/22/17
2,863 8/15/18 (??)

Unitarianism: "But there’s nothing in there"

Unitarian Humour

Lisa: “What flavours do you have?”

Rev. Lovejoy: “Well, chocolate, vanilla, strawberry, and our new Unitarian flavour ice cream.”

Lisa: “I’ll have that” (Rev hands her an empty bowl)

Lisa: “But there’s nothing in there.”

Rev: “Eeeexactly.”
Comment: Yet some people love it

Tesla's ca$h burn rate

Tesla’s Burning Through Nearly Half a Million Dollars Every Hour


Over the past 12 months, the electric-car maker has been burning money at a clip of about $8,000 a minute (or $480,000 an hour), Bloomberg data show. At this pace, the company is on track to exhaust its current cash pile on Monday, Aug. 6. (At 2:17 a.m. New York time, if you really want to be precise.)

To be fair, few Tesla watchers expect the cash burn to continue at quite such a breakneck pace, and the company itself says it’s ramping up output of its all-important Model 3, which will bring money in the door. Investors don’t seem concerned. Tesla shares rose almost 3 percent to $317.81 Tuesday, giving it a market capitalization of $53 billion. Ford Motor Co. is worth $48 billion.
Comment: See Electric Cars the Future? Not so Fast!
If electric cars are ever to displace gasoline engines without government putting its thumb on the scale, they must not only keep innovating but outrun fossil fuels where productivity also keeps advancing.

Electric cars have come a long way. They are no longer ugly, impossibly expensive and impractical, thanks to technological advances that have slashed battery storage from $1,000 per kilowatt-hour in 2010 to $273 per kwh last year, according to Bloomberg New Energy Finance.

Nonetheless, that means a 75 kwh battery (about what you need for 250 miles of range) still adds about $20,000 to a car’s cost. So how do the cars sell? Public largess helps a lot.

The federal government offers a tax credit of up to $7,500 each for the first 200,000 electric or plug-in hybrid cars a manufacturer sells. Throw in state tax credits, subsidies for recharging infrastructure, relief from gasoline taxes, preferential lanes and parking spots and government fleet purchases, and taxpayers help pay for every electric car on the road.

What happens when the credits go away? When Hong Kong slashed a tax break worth roughly $55,000 for a Tesla in April, its sales ground to a halt. In Georgia, electric vehicle sales plummeted 80% the month after a $5,000 tax credit was repealed.