公私合夥自上個世紀末以來快速發展，所採用的形式從民營化到合約委外等所在多有，學者間對公私部門角色、公私合夥制度的成效以及相關責任權屬等均有激烈的論辯。畢竟公私合夥隱含了將原本屬於「公」的權利轉移到了「私」的手上，公部門某種程度上逃避了原本應該承擔的責任與義務，且相關制度對此常常亦是模糊不清。
公車服務作為一種重要的公共服務，目前在許多先進國家仍由公部門負責提供，儘管可能虧損嚴重且營運績效不佳。英格蘭是少數由民營業者提供公車服務的先進國家之一，其制度可大致分為大倫敦地區的競標系統與倫敦外地區的解除管制系統，自1980 年代中期開始施行至今，兩種制度各有其優勢與課題。倫敦外地區解除管制後，儘管營運成本顯著降低，但地方政府卻不再能夠掌控地方公車路網，只能透過補貼來提供業者不願提供但有社會需求的路線，且補貼的幅度正逐年增加；對此，英國政府亟欲讓公私部門建立更為緊密的夥伴關係，由公部門提供軟硬體設施（如公車優先設施等），以換取業者更多更好的公車服務；另外，並試圖引入新制度，使地方政府重新掌握規劃路網的能力。大倫敦地區的競標系統使得公部門仍舊掌握路網規劃的能力，且有更充分的資源與人力進行監督管理，乘載率亦不斷上升；但鑑於大倫敦地區得天獨厚的社經條件，競標系統並不見得能適用於其他國家。
我國地方公車服務分為市區客運與公路客運，目前幾乎均由民營業者營運。本研究針對未定期進行評鑑的南部區域縣市，探討公部門如何對民營業者課責以及可能衍生的課題。研究發現，儘管部分主管機關曾經辦理評鑑，但卻從未對評鑑結果採取具體的獎懲措施，使評鑑本身失去了課責的意義。而在評鑑不具實質效力的情況下，補貼考核才是最主要的課責機制，這主要是因為業者必須仰賴政府給與的補貼款項；然而在行政資源有限下，如何發揮最大的效用仍有待改進。另外對公路客運而言，主管機關為中央政府，地方政府既無正當性亦無資源，使其不具有任何路網規劃或規範管制業者的能力，在強調因地制宜的治理概念下，地方政府的「無能」成為了不可小覷的課題。
本研究進一步建議，我國地方公車服務應採取更適當的市場進入與離開機制，透過如競標引入某種程度的競爭並配合長期特許權的模式降低行政資源的耗費；第二，公私部門應有更緊密的夥伴關係，這需要雙方更明確地認知各自的能力與責任，公部門負責軟硬體設施的提供，私部門負責改善服務本身；第三，我國制度賦予主管機關相當多樣的課責工具，但若使用不當只會造成資源浪費，故應將資源集中於最為有效的課責工具，即補貼考核；最後，地方政府應承擔更多地方公車服務提供的角色，特別是公路客運，例如鼓勵地方政府提案競標有限的補助金額，以發展最適合當地的公車服務提供模式。

Since 1970s, Public-Private Partnerships (PPPs) have been growing more and more attractive to many countries－taking the form from contracting-out to privatization－to deliver almost all kinds of infrastructures and public services which seemed to be the responsibilities of the Government before. But PPPs also induced intense debates among competition, risk transfer, efficiency, effectiveness, and, most of all, accountability, arguing that PPPs imply some shared responsibility for outcomes of their activities and can make accountability for decisions difficult to ascertain for the average citizen or even for oversight organization.
As an important kind of ‘traditional’ public service, in most of developed countries, local bus service is still delivered by public sector today. But in England, private firms are the principal provider (and so in Taiwan). The major impacts of the deregulation outside London and the tendering system in London are reviewed in this study. Outside London the cost dropped dramatically, but meanwhile the local authorities has lost almost all capacities to control or steer the local bus service networks, and can only provide supported services where no private firms would like to provide. However, the amount of all kind of grants is increasing in recent years. As a result, the central government is keen to bring back some power to local authorities although some new mechanism introduced in the Transport Act of 2000 did not work well. In contrast, London Transport still has the power for local bus network planning and regulation, along with much more resources than those outside London. These strengths have all contributed to a lot higher ridership in London. But concerned with the unique socio-economic environment of London, this successful tendering system may not be duplicated to other countries or even other areas in England.
In Taiwan local bus is divided to urban bus and intercity bus. This study uses the accountability framework to analyze the interaction of public and private sector in the local bus service delivering, and tries to figure out the possible issues and strategies. The result shows that, one of the main accountability mechanisms－performance assessment－does not work at all, and subsidy assessment becomes the most powerful mechanism although the effectiveness of subsidy assessment is largely restricted by the limited resources. As regards intercity bus especially, the local government almost has no capacity on it, and even if there exists some grants, most local government did not use it other than bus shelter.
This study argues that, first, the urban bus and intercity bus must apply a more appropriate mechanism for market entering and leaving, saying that, a hybrid of long term exclusive franchises and periodically tendering system. Second, the public and private sector should build on a more collaborative partnership, where bus operators invest in higher-quality services, while local authorities invest in traffic management schemes that give buses priority or in better bus stations, shelters and other facilities for passengers. Third, the limited resource should spend on the most effective accountability mechanism (i.e. subsidy assessment) to achieve better value for money. And in the last, local authorities must occupy a more important role in local bus service delivering, for example, through bidding the grants offered by the central government. Local solutions should be allowed to develop to suit local circumstances, rather than a single approach imposed everywhere.

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