The former leader of Lincolnshire County Council has been jailed for 18 months after being found guilty of misconduct in public office.
The jury took just over 10 hours to find Speechley guilty
Jim Speechley was ordered to pay £25,000 towards the prosecution costs and will not receive any assistance from legal aid.
The 67-year-old from Crowland had denied the charge.
The jury at Sheffield Crown Court returned a unanimous verdict after the eight-week trial.
The court heard how Speechley tried to influence the route of the A1073 Spalding to Eye bypass.
The jury was told he wanted to increase the value of a 4.21-acre plot that he owned in the area by increasing its potential for development.
Speechley has since sold the land - which the prosecution said would increase
in value by £17,500 to £375,000 if developed.
But Speechley said it "never crossed his mind" the field would increase in value.
The jury heard how Speechley, who spent 38 years in local government, told a
council engineer that he wanted the new road to cut into countryside to the east
The court was told he failed to publicly declare his personal interest in the route until after the police were brought in to investigate some 18 months later.
In mitigation, William Harbage QC agreed that Speechley had influenced the
route of the road but claimed he only wanted to help achieve the best outcome
for his constituents.
He said Speechley had "lost everything" since the investigation began.
"He's lost his good name, his reputation, his good character and whatever respect he had earned over the years.
"Forty years of public service has effectively been thrown away."
He added that there had been no loss to any individual or the general public
and said the bypass was still going ahead, with work expected to begin in July
It took the jury just over 10 hours to reach its verdict.
The judge said: "When such conduct is found proven, the court is bound to take a serious view - the public must have confidence in our servants".