Plaintiff, Carl Campbell, was employed by defendant, City of Troy, as its Superintendent of Public Works from June 15, 1959, until his mandatory retirement on December 31, 1967. Plaintiff received an annual salary for his services. The demands of the job required him to work *536overtime on numerous occasions. Plaintiff received no payment for this overtime work. Instead he accumulated compensatory time. At his retirement, plaintiff had accumulated 966-1/2 hours of compensatory time. He was paid for 80. He now seeks payment for the remaining 886-1/2 hours for which he received no compensation. The trial judge entered a judgment of no cause of action. We granted plaintiff leave to appeal.
When plaintiff began his employment defendant had in effect an administrative regulation governing payment of overtime. It provided that:
"Salaried employees shall not be entitled to overtime pay but may receive compensatory time-off on the basis of records kept by the department head and approved by the City Manager.”
In 1960, defendant adopted a new regulation with regard to overtime. This regulation divided city employees into two groups. Plaintiff was then and at all times until his retirement a member of Group 2.1 The pertinent regulation provided:
"Group 2 employees shall not receive overtime pay but may receive compensatory time-off on the basis of records kept by the department head and approved by the City Manager. Compensatory time shall be granted for all hours worked in excess of 40 hours per scheduled work week. For approved holidays worked during the scheduled work week, compensatory time shall be granted equal to the number of hours worked.”
On January 10, 1966, defendant city adopted Resolution #66-33(A). The applicable paragraph reads as follows:
*537"Employees in the Unclassified Service may not accumulate more than 80 hours of compensatory time. All compensatory time earned by employees prior to the adoption of these rules shall remain credited to them. Such employees, however, with more than 80 hours will be prevented from accruing additional hours. All compensatory time taken will be deducted from the total amount of compensatory time credited to the employee while no overtime worked will be added to the total until such time as the total compensatory time credited to the employee is reduced below 80 hours. Compensatory time will be taken off at a straight time ratio and such time off must be authorized by the City Manager.”
Pursuant to these regulations, plaintiff accumulated 1,330-1/4 hours of compensatory time prior to the adoption of the 1966 resolution. Subsequent to this he reduced the number of hours to 966-1/2. He now contends the defendant has a duty to pay him in monies for any accumulated compensatory time off he was unable to take prior to his mandatory retirement. The basis of his contention is the existence of an implied contract in law between himself and the city. He bolsters his argument by emphasizing the inequities of the situation. Justice can only be achieved by imposinq a duty on the city to pay for the benefits it has received as a result of plaintiff’s extra service. Cascaden v Magryta, 247 Mich 267 (1929); In re Camfield Estate, 351 Mich 422 (1958); Detroit v Highland Park, 326 Mich 78 (1944).
Appealing as plaintiff’s argument seems, closer examination finds it to be legally flawed. A contract will be implied only where no express contract exists. There cannot be an express and implied contract covering the same subject matter at the same time. Superior Ambulance Service v Lincoln Park, 19 Mich App 655 (1969). Plaintiff concedes that the regulations adopted by the de*538fendant city constituted an employment contract between the parties which governed the payment of overtime. The cases which plaintiff relies on have no application to the instant situation. All three involve situations where no express contracts were proven. See Cascaden v Magryta, supra; In re Camfield Estate, supra; Detroit v Highland Park, supra.
To determine whether plaintiff is entitled to monies in lieu of his unused compensatory time, we must look to the city ordinances and regulations which comprised the employment contract. If these ordinances and regulations do not provide for payment of the monies claimed, then plaintiff’s claim must fail. Olson v Highland Park, 312 Mich 688 (1945).
The applicable ordinances and regulations clearly indicate that at no time during his employment was plaintiff entitled to overtime pay. Any overtime worked could be compensated for in time off. The real issue before us is whether plaintiff had a vested right to be paid for unused compensatory time upon termination of his employment with the defendant. On this point, the ordinances and regulations are not clear.
Plaintiff bases his argument on the following language from Resolution #66-33(A): "All compensatory time earned by employees prior to the adoption of these rules shall remain credited to them”. Plaintiff contends that by using this language and by paying him for 80 hours, the city recognized his right to be paid for all his unused compensatory time. We agree that this is one possible interpretation of this language. We do not believe it is the correct interpretation.
Prior to the passage of Resolution #66-33(A), no limit was placed on the number of compensatory *539hours an employee could accumulate. The language on which plaintiff relies appears to he recognition by the defendant of the inequities that would have resulted had it stripped employees in plaintiff’s classification of hours they had accumulated in excess of the 80-hour limitation. There is nothing in the language of the 1966 resolution approving the payment of any monies for unused hours. It is important to note that plaintiff has offered nothing to counter defendant’s argument that prior to 1966, employees were not paid for their unused compensatory time at termination. Only after Resolution #66-33(A) was passed did this practice begin. In fact, when he retired, plaintiff accepted defendant’s payment for 80 hours without complaint. Further, plaintiff participated in drafting the 1960 regulation and argued at that time for changing the word "may” to "shall”. This indicates he understood that taking compensatory time off was not a matter of right. Given the history of the ordinances and regulations in question and the understanding of how overtime was to be paid to employees in plaintiff’s position which existed during the years of his employment, we cannot say that defendant’s interpretation of the challenged language is unreasonable or incorrect. See Satterley v City of Flint, 373 Mich 102 (1964). Plaintiff has no vested right to be paid for his unused compensatory time.
Plaintiff nevertheless contends that defendant should be estopped from denying a duty to pay him for the time in question. He claims that this estoppel is created by the city’s having accumulated his compensatory time over the years, giving him notice of the accumulated time annually, and allowing him a portion of this time as time off during his employment. We cannot accept this *540argument. An estoppel arises only when a party acts to induce another to believe that certain facts exist and the other rightfully relies and acts on such a belief to his detriment if the former is allowed to deny such facts. Holt v Stofflet, 338 Mich 115 (1953). Plaintiff has not proven nor alleged any action on the part of defendant or any of its officials which induced him to believe that he would be paid for his unused compensatory time at retirement. This is not a proper case for invoking the estoppel doctrine against defendant.
Affirmed.
Lesinski, C. J., concurred.In 1964 the City of Troy adopted a civil service ordinance. Under its terms, plaintiff's position was exempted from civil service protection.